The Virtual Customer

Communication and information technologies are adding new capabilities for rapid and inexpens ive customer input to all stages of the product development (PD) process. In this article we review six web-based methods of customer input as examples of the improved Internet capabilities of communication, conceptualization, and computation. For each method we give examples of userinterfaces, initial applications, and validity tests. We critique the applicability of the methods for use in the various stages of PD and discuss how they complement existing methods. For example, during the fuzzy front end of PD the information pump enables customers to interact with each other in a web-based game that provides incentives for truth-telling and thinking hard, thus providing new ways for customers to verbalize the product features that are important to them. Fast polyhedral adaptive conjoint estimation enables PD teams to screen larger numbers of product features inexpensively to identify and measure the importance of the most promising features for further development. Meanwhile, interactive web-based conjoint analysis interfaces are moving this proven set of methods to the web while exploiting new capabilities to present products, features, product use, and marketing elements in streaming multimedia representations. User design exploits the interactivity of the web to enable users to design their own virtual products thus enabling the PD team to understand complex feature interactions and enabling customers to learn their own preferences for new products. These methods can be valuable for identifying opportunities, improving the design and engineering of products, and testing ideas and concepts much earlier in the process when less time and money is at risk. As products move toward pretesting and testing, virtual concept testing on the web enables PD teams to test concepts without actually building the product. Further, by combining virtual concepts and the ability of customers to interact with one another in a stock-marketlike game, securities trading of concepts provides a novel way to identify winning concepts. Prototypes of all six methods are available and have been tested with real products and real customers. These tests demonstrate reliability for web-based conjoint analysis, polyhedral methods, virtual concept testing, and stock-marketlike trading; external validity for web-based conjoint analysis and polyhedral methods; and consistency for web-based conjoint analysis vs. user design. We report on these tests, commercial applications, and other evaluations. THE VIRTUAL CUSTOMER PAGE 1 The Virtual Customer Introduction New communications and information technologies such as the Internet, the World-Wide Web (web), and high-speed, broadband connections are transforming product development (PD). The PD process itself is transforming into an activity that is dispersed and global with crossfunctional PD team members spread across multiple locations and time zones and interconnected through a services marketplace. For example, Wallace, Abrahamson, Senin, and Sferro [85] report on a system that enables engineers to redesign critical components in weeks or even days – redesigns that once took six months. These and other changes put an emphasis on fast and accurate input from a variety of sources, including rapid input from customers [1, 13, 14, 20, 32, 52, 67]. At the same time, today’s spiral and stage-gate processes require input from customers iteratively at many times during the development process including the rapid evaluation of ideas early in the process, the identification of important “delighter” features as the product concept is refined, detailed measures of the importances of customer needs as the product is engineered, and accurate evaluation of prototypes as the product nears pretest and test marketing [11, 12, 15, 16, 37, 52, 53, 66, 73, 77, 87]. While information technology transforms internal PD processes within firms, it also impacts firms’ external interactions with potential consumers of new products. Customers’ broadband connections at home and work, combined with emerging Internet panels of willing respondents, mean that PD teams can reach customers more quickly and, ultimately, less expensively. Media rich computing and communication mean that product stimuli can include more realistic virtual prototypes and more realistic product features. And powerful, server-based software and downloadable applets mean that web-based methods can be more adaptive to customer input and change questioning procedures on the fly. In this article we review six web-based customer input methods. For simplicity, we call this set of methods the “virtual customer.” Some of these methods simply move paper-andpencil or centrallocation interviewing methods to the web. Others exploit the new communications and computing power to provide capabilities that were not feasible previously. Each of these methods has been implemented and pilot tested and some of the methods have been used to design products that have now been launched. However, we caution the reader that web-based THE VIRTUAL CUSTOMER PAGE 2 methods of gathering customer input continue to evolve. We and other researchers continue to test these methods in new applications and to explore new web-based methods to discover their strengths and weaknesses. In some applications, the virtual customer methods will replace exis ting methods, but in most instances they will complement existing methods for expanded capability. We organize the article as follows. We begin with a discussion of the three dimensions of web-based customer input. This structure is useful to (1) show how the web-based methods complement traditional market research and (2) suggest how web-based research will evolve. We then describe each of the six methods providing examples and, when they are available, initial applications and tests. Finally, we review how each method can be used in the various stages of an iterative PD process. Demonstrations of these methods, open-source software, technical reports, and theses are available at the virtual-customer website: mitsloan.mit.edu/vc. Communication, Conceptualization, and Computation Figure 1 depicts three capabilities of web-based customer input. The capabilities extend and enhance the trends that we have seen over the past ten years as computer-aided interviewing (CAI) has enhanced traditional telephone and centrallocation interviewing. The web has made these capabilities more powerful and is putting these capabilities directly into the hands of the PD team. Communication includes much more rapid interaction not only between the PD team and the respondents, but also between the respondents themselves. PD-team-with-respondent communication reduces the time required to conduct studies, and enhances understanding of the respondents’ task through interactive, hyperlinked help systems incorporated into the website. With this rapid communication it is now theoretically possible to gather sophisticated market information in a few days rather than the 4-6 weeks that are typical with traditional methods. For example, we completed a user design study of over 300 respondents over a weekend. To get to customers quickly, both new and traditional market research firms are forming panels of web-enabled respondents who can complete online tasks. National Family Opinion Interactive, Inc. (NFOi) has a balanced panel of over 500,000 web-enabled respondents. Digital Marketing Services, Inc., (DMS), a subsidiary of AOL, uses “Opinion Place” to recruit respondents dynamically and claims to be interviewing over 1 million respondents per year. Knowledge Networks has recruited 100,000 Internet enabled respondents. Greenfield Online, Inc. has THE VIRTUAL CUSTOMER PAGE 3 an online panel of 1.2 million households (3 million respondents). Harris Interactive, Inc. has an online panel of 6.5 million respondents [4, 25, 56]. These market research firms are aware of the fact that the Internet is still diffusing and are competing on ways to ensure representativeness of these panels. For example, NFO has had fifty years of experience balancing their traditional panels and NFOi is using that same techno logy to balance its Internet panel. DMS reports on 150 side-by-side tests of online vs. phone/mail/mall interviewing and states that “a rather extensive body of comparability work documents the consistent business direction finding [25].” Gonier [25] presents data that the DMS respondents have demographics close to the US population and can be balanced to match the US population. Knowledge Networks addresses representativeness by recruiting respondents with random digit dialing methods and provides them with web access if they do not already have it. In a more independent test, Willkie, Adams, and Girnius [86] conducted 50 parallel tests and found a high degree of correlation between mallintercept and web-panel respondents. These panels also make it possible to gather customer input in multiple countries simultaneously. For example, Harris Interactive claims panelists in 200 countries and Greenfield Online claims panelists in 162 countries [56]. Our own experience with NFOi suggests that it is relatively easy to field studies in multiple languages simultaneously. Although independent representativeness tests are still rare, we can take confidence in the fact that firms such as Apple Computers, Avon, Beecham, BMW, Hewlett Packard, IBM, Kodak, Microsoft, Pfizer, Procter & Gamble, Ralston Purina, and Xerox now use these panels (www.nfoi.com, www.greenfield.com). In fact, General Mills now claims to do 60% of their market research online [50]. As of this writing, these panels have focused on the consumer market. Although Harris Interactive does have a successful physician panel, recruiting has proven much more difficult for business-to-business panels. To date, most of the business-to-business on-line interviewing has required study-specific recruiting, thus mitigating some of the cost and time advantages. However, cost and time might decrease with experience and competitive pressure. To help PD teams implement studies quickly, application service providers (ASP’s) are developing web-based menu-driven systems by which teams can create customized surveys. For example, Faura [23] demonstrates a system in which a PD team member need only visit a website to choose the features and feature levels to be tested in conjoint analysis. The website then THE VIRTUAL CUSTOMER PAGE 4 sets up the web-page to which respondents can come, sets up the database, and provides analysis summaries – all automatically. Faura’s system is only a proof-of-concept rather than a commercial system, but other ASP’s, such as zoomerang.com, are now in common use for web-based surveys, and Sawtooth Software, Inc. has recently announced commercial software for the design of web-based interviewing systems. The web also facilitates respondent-to-respondent communication that might also improve the quality of information gathered, particularly for product categories (e.g., automobiles and communication devices) in which customers may influence one another’s choices. Realtime respondent-to-respondent communication can inform inter-subjectivity just as the widespread availability of real-time stock market quotations informs individual traders about the state of the financial world. PD teams can now observe respondent-to-respondent interactions to gain insight into customer needs and better estimate a new concept’s potential. Although respondentto-respondent capability has always been possible in face-to-face interviews such as focus groups, the web enables this communication to take place among larger numbers of customers and web-based interviewing enables the PD team to gather this information more rapidly. Additionally, web-based methods such as the information pump and securities trading of concepts are designed to be less susceptible to social influences than in-person focus groups. There is, however, a downs ide to rapid communication. With customers providing feedback online from the comfort of their homes or workplaces, the alternative uses of their time are high. Unlike in a central facility, web-based respondents are free to terminate the interview if they are bored or if they do not feel that the incentives (if any) justify their time. It is more difficult for some web-based survey methods to obtain the same response rates as mail/phone/mall interviewing. A web-based environment places a premium on interfaces that are interesting and engaging and which gather information using as few questions as is feasible. It is not enough to simply port existing methods to the web; they must be designed with the web in mind. Conceptualization utilizes the graphic and audio capabilities of multimedia computers to depict virtual products and product features. Concept evaluation has long been possible with physical prototypes, but such methods are expensive and time-consuming [47, 55, 58, 65, 79]. With rich virtual prototypes, PD teams can test their ideas and preliminary designs earlier in the process, well before physical prototypes are built. Although prior research has used virtual prototypes and information acceleration in centrallocation interviewing [78, 81 and Sawtooth THE VIRTUAL CUSTOMER PAGE 5 Technologies’ multimedia Sensus capability, www.sawtooth.com], these capabilities are now becoming available on the web. Further, new software and hardware is making the multimedia prototypes easier to develop and more realistic. These interactive, media-rich depictions also enhance respondents’ understanding and enjoyment of the task. Conceptualization may include multiple sensory inputs such as 2-D and 3-D visualization, interactivity, sound and music, and, eventually, touch, smell, and even taste through peripherals that are now being developed. Even for products or prototypes that exist in physical reality, virtual depictions have a cost and speed advantage over physical prototypes. Naturally, PD teams realize these advantages only if the data collected based on virtual prototypes replicates that which can be obtained with physical prototypes, and only if web-based interviewing replicates that which can be obtained with more traditional centrallocation interviewing. Although capabilities will improve with further experience, the initial tests reported in this article suggest that sufficient accuracy and reliability can be obtained. Computation enables improvement over fixed survey designs by dynamically adapting web-pages in real time, based on mathematical algorithms, while participants are responding. For example, adaptive conjoint analysis (ACA) has long adapted paired-comparison preference questions to each respondent based upon their answers to earlier questions [29, 41, 57, 62]. Not only has ACA moved to the web, but more computationally intensive optimization methods (described later) are being used to select stimuli. Even the multimedia stimuli themselves can be created on the fly. Suppose that the PD team was considering 50 alternative features for a product. Even with an efficient experimental orthogonal design for this 2 problem, the number of stimuli that would need to be created would be huge. With today’s software tools that enable layering of “puzzle pieces,” we can now create stimuli automatically as they are needed. Real-time computation also enables stimuli to become dynamic, interactive, and more informative. For example, instantaneous computation of price and performance as a function of design choices provides key feedback during the user design process. In this way, the end-user can better learn about tradeoffs and his or her personal preferences, thereby improving the accuracy of decisions about an “ideal design.” Virtual Customer Methods We now describe six virtual customer methods representative of the type of web-based customer input systems that are evolving. We chose these six methods as representative of the THE VIRTUAL CUSTOMER PAGE 6 space of current virtual-customer methods. These methods differ in the extent to which the question selection is fixed or adaptive and in the extent to which the method focuses on product features versus fully integrated product concepts. See Figure 2. Each method has been implemented in a working system and has been applied with realistic stimuli, some as part of commercial PD processes. We provide perspectives on the advantages and challenges of each. We invite the reader to combine aspects of these six methods and, perhaps, create new, customized methods just as product designers often select the best features from multiple concepts and incorporate them into a final design (e.g., [61]). We also expect that each of these methods will evolve with further experience and as the communication, conceptualization, and computational capabilities of the web increase. We hope that refinements of the initial versions presented here will fully empower cross-functional teams to explore multiple design solutions and tear down the barriers between engineer/designers and end-users. Figure 3 summarizes the six methods and highlights how each of the current implementations exploit communication, conceptualization, and computation. We begin with web-based conjoint analysis (WCA) as an example of how traditional customer feedback systems are moving to the web. Web-based Conjoint Analysis (WCA) Conjoint analysis has been the subject of intense academic research for over twenty years [cf. 30, 31]. Basically, in a conjoint analysis study, products or product concepts are represented by their features, where each feature can have two or more alternative levels. The goal of the study is to find out which features and feature levels customers prefer and how much they value the features. For example, a new instant camera might be represented by features such as image quality, picture taking (1-step or 2-step), picture removal method (motorized ejection or manual pull), light selection method, and two styling attributes – opening (slide open or fixed) and styling covers (Figure 4). Other features such as picture size, picture type, camera size, battery type, etc. might either be assumed constant among all concepts under study or might be the focus of a separate study. The data collection and analysis procedures are many and varied. For example, product profiles might represent a factorial design of the feature levels and the respondent might be asked to rank order all profiles in terms of preference. Alternatively, respondents might be presented with many groups of attribute bundles and asked to select one from each group, or, they might be given pairs of concepts and asked to select between the two concepts. Hybrid THE VIRTUAL CUSTOMER PAGE 7 methods ask customers to rate the importance of the features directly and then update those importance measurements with data from profile ranks, choices, or paired comparisons. All of these methods work with either rank-order data or a rating scale that is designed to measure the intensity of preference. Although new analysis methods are being developed that exploit new computational algorithms (described later), the primary focus in web-based conjoint analysis has been the user interface. Among the challenges are (a) the limited screen “real estate” of most computer monitors which constrains the number of profiles that can be viewed, (b) the limited time and concentration that most respondents commit to the task, and (c) the fact that instructions and tasks must be understood without the researcher present. On the other hand, the web offers multiple benefits including: (1) enhanced stimuli that are visual, animated, interactive, and hyperlinked, (2) flexibility to enable respondents to participate at their convenience from the comfort of their homes or workplaces, and (3) the engaging ease and speed with which respondents can express their preferences through simple clicking, without requir ing typing. An effective user interface exploits web-based benefits to address the challenges as they relate to: the respondents’ task, the number of features, the number of levels, the number of stimuli, and the depiction of concepts. We illustrate two web-based interfaces. The first collects paired-comparison data and the second gathers ranks on full profiles of features. These methods are extendable to customization with self-explicated importance ratings, other intensity measures, or choice-based tasks. The paired-comparison study [51] explored the six features of an instant camera (Figure 4) targeted at preteens and teenagers. Because this was a pilot test of the method, the interface was programmed in HTML specifically for this application. However, this study did demonstrate that web-based interviewing could be used for products targeted at difficult-to-reach respondents such as children. 1 Because the concept of a postage-stamp size picture was relatively new at the time of the study and because many of the features required visualization, the study began with interactive screens that introduced the product and its features. For example, in Figure 5 respondents click on any image to get a demonstration of the product’s use – say customizing your math textbook with an image that illustrates how you feel about the subject. Applets enable respondents to observe picture quality, how the camera opens, how photos are ejected, etc. Post analysis sugTHE VIRTUAL CUSTOMER PAGE 8 gested that the children enjoyed the task (“kind of fun”) and found it to be about the right length [51]. After the productand featureinstruction screens, respondents completed the pairedcomparison task in Figure 6. The task was made easier for the respondent by animating the 9point scale and by making detailed feature descriptions or product demonstrations available with a single click. While paired-comparison questions fit the need for clarity and limited screen size quite well, pretests and prior studies suggested that they became monotonous after 10-15 questions [8]. Thus, the children were asked only eight paired-comparison questions. This limited the data analysis to aggregate (segment-level) estimates of feature importance and concept share. While this was sufficient for the application in which only six features (plus price) varied, it became clear to both the firm and to us that new adaptive methods were necessary for more complex problems. These methods are described later in this article. The application was considered a success by the firm. The PD team felt that the data had high face validity and internal consistency. Because the firm had previously relied on mallintercept interviewing, a parallel study was completed in which respondents were recruited in a mall and brought to a central facility to complete the conjoint analysis tasks. The partworth estimates from the two studies were highly correlated (0.80 correlation significant at the 0.01 level). Despite some slight differences, the basic managerial message was the same and implied the same camera design, thus suggesting that the more rapid web-based interviewing could substitute adequately for traditional mall-based interviewing. Furthermore, the percentage of respondents who answered the survey completely without task neglect was 85% in the mall and 86% at home suggesting that the interface was engaging and that the task was not too onerous. However, the percent of respondents who visited the website after being recruited was 38% suggesting a need for improvement relative to the 50% that is typical for telephone interviewing [89, 90]. The study identified at least one feature that was a “delighter” to teenagers, but not anticipated by the adult PD team – removable styling covers. The camera was launched as the “iZone Convertible Camera” with “fashion-forward faceplates” in multiple styles and colors (www.izone.com). The study also identified features that were not important to children and could be eliminated from the camera to keep the design within the price target. In particular, it THE VIRTUAL CUSTOMER PAGE 9 did not appear that teenagers valued a folding camera or one that ejected the pictures automatically. Full-profile Evaluation Interface for Web-based Conjoint Analysis (WCA) The paired-comparison task is ideally suited for CAI. It underlies Sawtooth’s widelyused version of ACA, and CAI conjoint examples with paired comparisons have been in the academic literature for twenty years (e.g., [35, 36]). However, ranks of full-profile concepts remain the most common form of conjoint analysis among practitioners accounting for over 60% of the applications [7, 46, 91]. Not surprisingly, ranking many concepts put s high demands on screen real estate and requires a creative user interface. Such interfaces are still being developed and refined; we present one that has now been applied for crossover vehicles, ski resorts, tape backup systems, digital cameras, automobile telematics, pocket PCs, high-speed color printers/copiers, and ultralight portable computers. Respondents find the task intuitive, interesting, and easy-tocomplete. We illustrate the task with “crossover vehicles” – car/trucks that combine the all-wheel drive and height of sport utility vehicles (SUV’s), the amenities and ride of luxury cars, and the interior flexibility of minivans. After much experimentation and pretest, we found that respondents were most comfortable seeing no more than twelve stimuli per screen. One such design is shown in Figure 7. (The squares in the upper left corner of each stimulus are color-coded to match the high vs. low levels of the product features. We found that such visual cues help the respondent complete the task more quickly.) The orthogonal design for crossover vehicles consists of 12 profiles from a 2 factorial design. For designs larger than twelve stimuli, this interface can be extended, up to the limit of respondent fatigue, by displaying multiple screens of up to twelve profiles per screen. Each profile “card” is an independent HTML file that is randomized on the screen. (Respondents see this screen after first being introduced to the product category and the features in an interactive fashion not unlike that described for the camera in Figures 4 and 5.) Pretests suggest that ranking all twelve images on one screen is difficult for respondents. Instead, we evolved the following set of tasks. • For each set of twelve stimuli, respondents click on those cards, in no particular order, that they would be “likely to buy.” Clicked cards disappear from the screen. • Respondents then click on cards that they would be “unlikely to buy.” THE VIRTUAL CUSTOMER PAGE 10 • Remaining cards are automatically added to a “not sure” group. • Respondents then rank order stimuli within each of the “likely,” “not sure,” or “unlikely” groups by clicking on profiles in order of preference. Each clicked profile disappears from the screen, so respondents are always clicking on their most preferred remaining profile. • The rare groups with more than twelve cards require scrolling within the browser window. • To check for errors and to iterate if necessary, respondents are asked paired-comparison questions that compare the least preferred “likely” profile to the most prefe rred “not sure” profile, and the least preferred “not sure” profile to the most preferred “unlikely” profile. • Finally, the “likely,” “not sure,” and “unlikely” groups are “stitched” together to create the rank order of all stimuli for analysis. In addition to the rank orders, this user interface also identifies “likely” and “unlikely” profiles with which to estimate minimum utility cutoffs. Such screening has been shown to improve estimation accuracy [49]. Initial tests of this interface suggest strong internal consistency. Groups of students and eBusiness executives yielded mean violated pairs (mean number of pairs of profiles ordered inconsistently with the estimated utility function prediction) of only 2.7% of the possible pairs as compared with the 12.6% that would result under a random ordering (n = 158 respondents in four separate studies). Although the interface is promising as a means to port full-profile conjoint analysis to the web, it is limited to six to ten features because respondents appear to have difficulty making simultaneous evaluations of more than this number of features and due to screen real estate constraints. Because conjoint analysis has a long history, we expect that the reliability and validity of web-based methods will be refined to match that of centralfacility methods. We provide one external validity test of the paired-comparison interface when we review the newer polyhedral adaptive conjoint analysis method in the next section of this article. The paired-comparison and full-profile user interfaces represent two web-based conjoint analysis applications that enable the PD team to get rapid feedback about feature importances from customers. Both applications have high face validity and provide valuable insight for the design of the product in question. However, to date, these interfaces are limited by potential respondent wear out and, hence, have been applied to relatively small designs. These are certainly not the only interfaces possible and, given the large academic and industry interest in conjoint analysis, we expect these interfaces to be refined over the next few years. Such refinement THE VIRTUAL CUSTOMER PAGE 11 should soon make it feasible to use web-based hybrid designs that can deal with the fifty or more parameters that are possible with centralfacility interviewing (cf. [88]). Fast Polyhedral Adaptive Conjoint Estimation (FastPace) Concern about respondent burden in conjoint analysis is not new. As early as 1978, Carmone, Green, and Jain [5, p. 300] cautioned that most conjoint applications required more parameters to be estimated than the number of profiles that customers could rank comfortably. Other researchers suggested that, due to respondent wear out, accuracy degrades as the number of questions increases [2, 27, 28, 39, 44, 48, 49, 54, 72]. Over the past twenty years many researchers have proposed methods to simplify the experimental design, simply the respondents’ task, eliminate profiles or features, and use hybrid methods that mix individuallevel and segmentlevel data (cf. [26, 70]). In particular, adaptive conjoint analysis (ACA) has enjoyed wide use. Green, Krieger, and Agarwal [29] claim that ACA has grown quickly to become one of the most widely used conjoint analysis methods. ACA seeks to reduce the number of questions required by using respondents’ earlier answers to customize later questions [62]. In ACA, respondents first state the importance of each feature (self-explicated phase) and then indicate their relative preferences between pairs of partial profiles (paired-comparison phase). The resulting utility estimates are then scaled to predict choice based on respondents’ self-stated probability of purchase for several full product profiles (purchase intention phase). In the adaptive phase (paired comparisons), profiles are chosen such that both profiles in a pair are nearly equal in utility, subject to constraints that make the overall design as orthogonal as possible. ACA has proven accurate under the right circumstances, and the adaptive phase has proven to add incremental information relative to the self-explicated phase of the interview [39, 40, 57]. In addition, Johnson [42] proposes that the accuracy of ACA can be improved by post-analyzing the data with a hierarchical Bayes algorithm. See further discussion in Green, Krieger, and Agarwal [29] who suggest when ACA is appropriate and when caution is due. To date, although ACA is a CAI system, most applications have required a central facility to which customers are recruited. Recently, Sawtooth Software introduced web-enabled ACA and claims seventy-five applications in beta testing of their web-based interviewing system which includes ACA as a tool (www.sawtoothsoftware.com). However, even with the adaptive portion, ACA does not fully solve the need for a reduced number of questions – a need that becomes more acute on the web due to the need to hold a respondent’s attention. If a conjoint THE VIRTUAL CUSTOMER PAGE 12 analysis study requires p parameters to be estimated – e.g., for p features at two levels each – then ACA requires approximately 3p questions: p self-explicated questions plus 2p pairedcomparison questions, as well as the purchase intent questions. While this is sometimes a dramatic improvement over non-adaptive methods, it might still be a large burden for the typical web-based respondent. Fortunately, new computation developments have the potential to improve adaptive conjoint questioning for web-based respondents. In particular, a revolution in mathematical programming begun by Karmarkar [43] in 1984 enables researchers to design robust heuristic algorithms that obtain excellent approximations to complex computational problems. Most importantly, these algorithms run extremely fast. These algorithms, coupled with today’s fast computers mean that adaptive paired-comparison questions can be found such that they provide conjoint-analysis estimates with fewer questions. In some cases, the self-explicated questions can be skipped entirely and good approximations can be found with fewer than p questions. While such estimates do not have the nice theoretical statistical properties of estimates based on least-squares or maximum-likelihood estimation, there is some evidence that when respondent fatigue is a concern, estimates based on fewer questions might actually be more accurate [74]. The heuristic algorithms are surprisingly accurate and hold promise when PD teams seek to identify quickly which features are among the most important. Hence, the fast polyhedral methods are most useful in the early stages of PD when the team is trying to winnow the list of important features of a new product in order to identify exciting new concepts. We describe here the concepts underlying one such “interior-point” algorithm based on proportional ellipsoids and the analytic center [24, 68, 69, 82]. Toubia, Simester, and Hauser [74] propose that each respondent be described by a vector of the relative importances that he or she ascribes to each of p features. If these importances are scaled between 0 and 100, then the feasible set of relative importances is a hypercube in p dimensions. The trick is to ask questions that shrink the feasible set of parameter values as quickly as possible. At any given point in time, say after q questions, the best estimate for a respondent’s feature importances is then specified by the analytic center of the remaining feasible set. The exact algorithm (and how the authors model measurement error) is beyond the scope of this article. However, the algorithm is sufficiently fast that respondents experience minimal computational delays between the pairedcomparison questions. THE VIRTUAL CUSTOMER PAGE 13 The algorithm was tested initially using Monte Carlo simulation of 1,000 respondents each for ACA, an efficient fixed factorial design, and the authors’ algorithm, which they dub FastPace (FP). In simulation, FP is more accurate than fixed designs for any number of questions up to 1.5 times the number of parameters and gets close to the “correct” answers in fewer questions. For example, after only ten questions FP’s mean absolute error is only 46% higher than that obtained with an efficient design of twenty fixed pairs. The comparison with ACA is more complex because ACA requires p initial self-stated importance questions. However, in one example the authors show that if the self-stated importances are relatively noisy, then FP can obtain the same accuracy in ten paired-comparison questions as ACA obtains in twenty pairedcomparison questions plus ten self-stated importances. If the self-stated importances are not noisy, then ACA is more accurate initially than FP, but a hybrid that incorporates self-stated importances into the FP algorithm is even more accurate than ACA. The authors conclude that FP is particularly promising when PD teams are limited to relatively few questions, when respondent wear out is a significant concern, and/or when self-stated importances are noisy. FP was then tested in a validation experiment by Dahan, Hauser, Simester, and Toubia [17]. Respondents compared pairs of laptop computer bags using an interface similar to that in Figure 6, with additional questions as required by ACA. The bags varied on nine features plus price. Approximately one-half of the respondents were randomly assigned to an FP-based survey (n=162), approximately one-fourth to an ACA-based survey (n=80), and approximately onefourth (n=88) to a survey based on an efficient fixed design. After completing the survey and then a filler task, the respondents were given the choice of five laptop bags that varied on features and price. (The five bags were chosen randomly from a factorial design of sixteen bags.) The choice was real – the respondents were given the bag they chose plus any change from $100. Respondents ranked all five bags under the belief that they would be given lower choices if their top choices were not available. Table 1 reports the results of validity tests. The first sixteen paired-comparison questions were chosen by the method being tested. Respondents then completed four additional pairedcomparison holdout questions, providing a test of internal validity. The external validity test compared the ability of each method to forecast the respondents’ choices of bags. Since the forecasts are based directly on the estimation of the importances of the products’ features, they implicitly test the ability of the various methods to accurately assign importances to product feaTHE VIRTUAL CUSTOMER PAGE 14 tures. Based on this initial experiment, FP appears to be significantly better (0.01 level) than both ACA and fixed designs for estimates based on eight questions and for estimates based on sixteen questions. Furthermore, the eight-question FP results appear to do as well as the sixteenquestion ACA or fixed-design results. Further analysis suggests that these estimates can be improved with at least two hybrid methods, one that combines self-stated importances with the FP algorithm and one that uses an alternative ACA estimation algorithm. Based on these tests, the new computational algorithms appear to hold promise for further developments that could enable PD teams to test more features with fewer questions. User Design (UD) We now turn to the final feature-based method that complements WCA and FP. Both WCA and FP exploit some of the web-based interactivity to provide estimates for each respondent of the relative importances of product features. These data enable the PD team to forecast customer reaction to any combination of product features, not just those tested directly. However, even with adaptive methods, the number of parameters that can be estimated is limited by the patience of the respondents. If features have interactions, such as a respondent valuing cargo capacity more in a seven-seat vehicle than in a five-seat vehicle, then even more questions must be asked to identify relative importances, ultimately leading to respondent fatigue. This further limits the number of features that can be tested. (For example, two independent three-level features require four parameters but two interacting threelevel features require eight parameters.) User design (UD) sacrifices the generality of conjoint-based methods in order to handle more features that might possibly interact. Because UD data gathers only the ideal feature combination for each respondent, it does not have WCA’s and FP’s abilities to simulate how respondents will react to any feature combination. However, UD can be used to determine which features are most desired by customers, which features interact, and which feature combinations are viewed as ideal by customers. In addition, the interface is enjoyable to the respondent and relatively easy to implement. It has been applied to cameras, copier finishers, laptop bags, automobile telematics, toys (GI Joe and Mr. Potato Head), custom shotguns, and laundry products. UD relies heavily on the web to exploit the proven ability of customers to design their own products. (See Urban and von Hippel [80] and von Hippel [83, 84] for examples of user input in the PD process.) THE VIRTUAL CUSTOMER PAGE 15 Specifically, the web provides user interfaces that enable customers to select interactively those features that they prefer in their ideal product. In many ways UD is similar to product “configurators” used by websites such as Dell.com and Gateway.com, in which customers order products by selecting features from drop-down menus. The key differences are (1) that UD uses real and virtual features in a visually integrated format and (2) that the displayed product changes interactively. These differences enable the PD team to determine which features to offer customers. Van Buiten [75] describes such an approach applied to the design of future helicopters, which improves on the usability of traditional configurators by enabling respondents to drag-and-drop (DnD) their preferred features onto a design palette that illustrates the fully integrated product. For example, in Figure 8 respondents are shown the same six camera features from Figure 5. Respondents indicate which features they want in their camera by dragging features from the “what you can buy” column to the “what your camera has” column. To remove features they drag features from “what your camera has” to “what you can buy.” As respondents make these choices, tradeoffs such as price, appearance, and performance are instantly visible and updated. The respondents iteratively and interactively learn their preferences and reconfigure the design until an “ideal” configuration is identified. The method can include full configuration logic, so that only feasible designs can be generated – choices on one feature can preclude or interact with choices on other features. For example, Figure 9 illustrates the use of UD in the design of a copier finisher. In this application, some features (C-fold and Z-fold) could not be chosen simultaneously. Beyond final feature choices, researchers observe click stream patterns and completion times. UD provides an engaging method of collecting data on customer tradeoffs. These data can be used to narrow the set of features or determine which features should be standard and which should be optional. The reduced set of features can then form the basis of a more extensive conjoint analysis. While UD may be especially appropriate for “lead users” who are open to exploring innovative solutions to address their acute needs [83, 84], we have found that the method works well with “normal” users (even kids), once they have been briefed (via the web) on the solution space and potential benefits of the product. If PD teams are to use UD for the rapid screening of features, we would like to know whether or not UD provides data that are consistent with the more intensive WCA and FP methTHE VIRTUAL CUSTOMER PAGE 16 ods. Specifically, how well does UD identify important features and predict customer choice? We begin by examining internal consistency with data from the camera WCA. Recall that only eight WCA paired-comparison questions were asked per respondent in Figure 6, thus, we could only obtain estimates of feature importance at the segment level. Because there were no significant differences found among segments (male vs. female, pre-teen vs. teen) we compare populationlevel estimates. In a parallel camera UD we recorded the number of customers who included each of the six features in their ideal design. These percentages are shown on the horizontal axis of Figure 10. To place the WCA estimates on the same scale we used logistic regression to map the partworth values and price to the choice percentages. These are shown on the vertical axis of Figure 10. The correlation was quite high (0.91) and was significant at the 0.01 level. Although the camera UD-WCA comparison demonstrated consistency in a real product that is now launched, it was limited to the aggregate level only. To test the consistency of UD with WCA we completed two additional tests. One was based on the copier finisher in Figure 9 and another was based on the crossover vehicles in Figure 7. In each case we used WCA to estimate feature importances and price sensitivity for each respondent and used that data to predict whether or not they would select that feature at the price shown in the UD. The WCA for the copier finisher was based on an older interface similar to that used in virtual concept testing (Figure 12). Respondents found this interface cumbersome for WCA and felt that this interface overemphasized price. This led to the improved interface that was illustrated with crossover vehicles (Figure 7). Thus, we were not surprised when the new interface was more consistent with UD than the old interface. In particular, the older WCA was able to predict feature preference correctly for 61.3% of the respondentfeature combinations (n=245 respondents x three features). This improved to 66.0% when we readjusted overall price sensitivity with a logit model. However, with the newer interface the ability of WCA to predict feature preference improved to 73.1% (n=130 respondents x six features) without any adjustments. All of these predictions are significantly higher than random at the 0.01 level. We also examined the consistency of UD and WCA by using feature importances from WCA to estimate a rank ordering of all potential UD combinations of non-price features, with price a function of the other features. In the crossover vehicle example, UD yielded sixty-four possible vehicle designs (2 possible configurations of six features at two levels each). Figure 11 THE VIRTUAL CUSTOMER PAGE 17 reports the percentile rank of the UD selection for each respondent – 60% of the respondents configured a vehicle that was in their top decile as predicted by WCA; 85% of the configurations were in the top quartile. Firms and researchers are just beginning to experiment with UD as a PD tool. Because respondents find the interface easy to use, enjoyable, and fast, UD has the potential for screening large numbers of features while highlighting interactions. For example, a UD for laptop bags highlighted that logos were more likely to be preferred on bags that were offered in respondents’ school colors and that those respondents who chose cell-phone holders were more likely to choose a PDA holder. In our applications we have assigned fixed prices to each feature, but prices are easily randomized to enable measurement of price sensitivity. Liechty, Ramaswamy, and Cohen [45] demonstrate one such approach in the context of a web-based Yellow Pages service, and show how multiple UD exercises allow estimation of part worths at the individual level. The UD interface is also beginning to be used by manufacturers who sell masscustomized goods over the web. One example is the website used by a laptop computer bag manufacturer, Timbuk2.com. UD capability also opens new research opportunities for academics and new persuasive tools for marketing professionals. For example, Cattani, Dahan and Schmidt [6] employ data from the laptop bag example to optimize mass customization. Park, Jun, and MacInnis [59] demonstrate that customers arrive at different “ideal configurations” depending on whether they are asked to add options to a base model or subtract options from a fully loaded model. As these phenomena are better understood, site designers might enhance sales effectiveness with the initial configuration of a UD website (in the case of mass-customized e-commerce). This developing research also cautions market researchers that initial feature levels that are presented to customers as defaults could influence measures of customer interest in features. Virtual Concept Testing (VCT) Not all products can be completely decomposed into features. For example, while the WCA in Figure 7 is useful to gain an understanding of how consumers value features in crossover vehicles, we would not expect those six features to fully describe a crossover vehicle. Styling is clearly important, as is brand and the manufacturer’s reputation for reliability and service. THE VIRTUAL CUSTOMER PAGE 18 Because holistic descriptions are critical to ultimate customer purchase decisions, PD teams often need to move beyond feature-based methods, especially later in the PD design process. In virtual concept testing (VCT), respondents view new product concepts and express their preferences by “buying” their most preferred concepts at varying prices. These choices are converted into preferences for each concept by conjoint-analysislike methods in which the rankorder selections are explained with the two variables, price and concept, as in Dahan and Srinivasan [19]. The interface is illustrated in Figure 12 where each of eight crossover vehicles are represented by brand name, pictures, and ratings on seven features. The respondent decides sequentially which concept they would buy at each of three prices, $25K, $35K and $45K. Because this method has already been published in the Journal of Product Innovation Management we refer the reader to Dahan and Srinivasan [19] who demonstrate that VCT preferences are highly correlated with concept tests based on physical prototypes. We replicated their approach with eight crossover vehicles using three independent groups of respondents, two student groups (n=43, 49) and a group of eBusiness executives (n=42), using the VCT task in Figure 12. The forecast market shares had high reliability (Cronbach’s α = 0.95) for both first-preference shares and for shares of the top three vehicles. Our experience suggests that VCT complements WCA, FP, and UD. While WCA, FP, and UD help the PD team identify the most important features, VCT enables evaluation of full concepts, complete with pictures and other multimedia representations. We expect VCT to grow in power and applicability over the next few years. With further development of multimedia concept representation, more realistic and practical CAD renderings, and increased Internet bandwidth, VCT methods have the potential to reduce the cost and time devoted to concept testing and/or to increase the number of concepts that can be tested earlier in the PD process. Securities Trading of Concepts (STOC) We now review two methods that exploit the web’s ability to enhance communication among customers and measure the preferences of a group of respondents. By structuring incentives carefully so that customers act in their own best interests, one method (Securities Trading of Concepts, STOC) uses the computational capability of web-based servers to monitor customer interactions in a manner that attempts to reveal customers’ “true” preferences. Another method (the Information Pump, IP) focuses on the language that respondents use to evaluate concepts THE VIRTUAL CUSTOMER PAGE 19 and features and, hence, provides an interesting complement to voice-of-the-customer methods [33]. These interactive, incentive-compatible “games” have the potential to address the criticisms of response biases and demand artifacts in survey research [63, 64]. Further, by observing customer-to-customer interaction, these methods might extend virtual customer methods to those products for which customers may be influenced by others’ opinions and choices – an externality that is not easily accounted for with traditional concept testing methods. Both methods are relatively new and, as such, we cannot yet report the same level of reliability and validity testing that is available for the customer-feedback methods. Instead, we present both methods as examples of the new ideas emerging from research on web-based customer-to-customer interaction. The STOC method sets up a market in concepts through which “traders” reveal market preferences as they buy and sell securities in a free market. A system implemented by Chan, Dahan, Lo, and Poggio [9] uses fifteen or more respondents who simultaneously log onto a secure website to engage in a trading game. Traders (respondents) are not asked their preferences directly. Rather each trader is told to maximize the value of his or her portfolio of concepts. Traders whose portfolios have higher values at the end of trading receive higher rewards. The trading begins with an introduction to the product concepts (securities) where product diagrams, photos, performance ratings, and textual information are provided in a web-based interactive format. Figure 13 provides two examples – bike pumps and crossover vehicles. After the securities briefing, traders are introduced to the STOC trading user interface in Figure 14. It includes a buy-and-sell order entry form in the upper right, transaction monitoring in the center right, a portfolio summary in the lower right, updated prices, spreads, and volumes in the lower left, and a stock-by-stock graphical history in the upper left. This interface simulates the capabilities available to Wall Street traders. Stock prices are strictly determined by exchanges between buyers and sellers. If the market is efficient, these valuations will depend upon traders’ personal evaluations of the securities, their expectations of others’ valuations, and the current price of each stock. The innovation here is that the securities represent competing concepts within a product category, similar to the Iowa Electronic Market (www.biz.uiowa.edu/iem/) in which securities represent political candidacies and the Hollywood Exchange (www.HSX.com) in which securities represent individual movies, actors, and directors. STOC uses the price mechanism to rapidly disseminate preference information to enable the “market” to value winTHE VIRTUAL CUSTOMER PAGE 20 ning and losing product concepts. STOC builds on the IEM and HSX approaches, adding the important element of virtual concepts including those that do not currently, nor might ever, exist. In an initial test of the STOC method, we compared the outcomes of several trading game experiments for a specific set of products with the outcomes of more traditional concept-testing methods for those same products. Specifically, nine portable bicycle pump concepts from Dahan and Srinivasan [19] were traded in two STOC games. The outcomes are plotted in Figure 15. Although the original preferences are based on a large sample survey of west coast students and the STOC (median) prices are based on a smaller sample of east coast students two years later, the top three “winners” are consistent across methods. The correlations between preferences and STOC median prices are 0.88 and 0.82, both of which were significant at the 0.01 level. STOC was then replicated using crossover vehicle concepts with two MBA student groups (n=43, 49) and a group of eBusiness executives (n=42). The market shares, as forecast using the STOC median price and the STOC volume-weighted average price, were reliable (Cronbach’s α of 0.85 for each measure separately; 0.94 for the combined measures). Although no external measure of market share was available, the shares forecast by STOC correlated well with first preference shares (0.74, 0.01 level). The potential advantages of STOC are (1) its ability to measure preference in situations where one consumer’s preference depends upon the “market’s” preference (e.g., products in which fashion and styling are important), (2) an ability to gather opinions quickly from customers through an enjoyable “game” experience, (3) incentive compatibility, and (4) several “price” measures indicating each concept’s relative strength. Initial tests suggest that securities trading can be taught to college-educated respondents quickly and naturally. However, STOC needs further testing prior to full-scale adoption. In particular, the authors plan further usability testing with a broader group of respondents and reliability and validity testing beyond that suggested by Figure 15. This testing should isolate the “price” measures that are most predictive of ultimate market shares. Experiments to date suggest that the closing prices and the maximum prices are subject to manipulation by experienced “gamers.” In contrast, median, minimum, and vo lumeweighted-average prices appear to be more accurate and robust predictors. Other experiments will vary the information given to the “traders.” For example, the traders can be given information from previous STOC tests and/or prior customer-feedback tests such as WCA, UD, FP, or VCT. THE VIRTUAL CUSTOMER PAGE 21 The Information Pump (IP) Most of the research on web-based methods has focused on the importance of alternative product features and on concept evaluation, but the ability of the web to enhance customer-tocustomer communication can also be used to learn the voice of the customer in new and creative ways. Prelec’s [60] information pump (IP) is a web-based customer input method that is focused on the fuzzy front end of product development when the PD team is trying to understand the vocabulary and descriptions that customers use for both existing products and new concepts. The IP is, in essence, a virtual focus group but with some interesting twists based on the computational capabilities of today’s web interfaces. In particular, the task and the incentives in the IP are fine-tuned so that the respondents think hard and provide honest answers. The initial applications of the IP have been in the context of concept tests – respondents are presented with virtual concepts, often with multimedia demonstrations, and are asked to describe these concepts. There are three roles in the “game” – encoder, decoder, and dummy. The encoders and decoders see the concept but the dummy does not. The dummy remains the dummy throughout the game, but the other respondents cycle through the roles of encoder and decoder. Encoder/decoders each see the same basic concept, but are given different photographs or renderings of the same concept. This way, when they communicate, they are forced to communicate about the fundamental characteristics of the concept, such as “the concept is a car for young people,” rather than superficial features, such as “the car is in the middle of the photo.” In any given round of the game, the encoder offers a true/false statement about the concept, and states whether the statement is true or false. For example, the encoder might state that a concept car is “good for city driving” and that the answer is “true.” The decoders then state whether they perceive the statement as “true” or “false” and indicate their confidence in their answer. If the concept really is “good for city driving” compared to an average automobile, then the decoders will answer true with high confidence. The dummy views the statement (but not the concept) and guesses the answer to the question. The dummy may or may not be able to guess the answer correctly and may or may not be confident in his or her answer. If the statement does not discriminate among cars (“has four wheels”) or if the statement is redundant with previous statements (“an urban vehicle”), then the dummy can guess the answers as well as the decoders. If the statement accurately describes the concept (i.e., is clearly true or false) and if the statement provides a new and different description relative to previous statements in the THE VIRTUAL CUSTOMER PAGE 22 game, then the decoders will be able to figure out the answer better than the dummy, and with higher confidence. To encourage truth telling, the decoders are rewarded on the accuracy of their answers. They are rewarded more if they are more confident. To encourage the dummy to think hard, the dummy is also rewarded on the accuracy and confidence of his or her answers. To encourage the encoder to generate non-redundant, descriptive statements, the encoder is rewarded on the accuracy and confidence of the decoders’ answers relative to the accuracy and confidence of the dummy’s answers. Detailed rules of the game, an example reward structure, and sample applications are available on the virtual customer website. Figure 16 illustrates a typical user interface. A discussion log keeps respondents informed of others' reactions and reinforces the rewards of the game. The specific reward structure and the psychology behind the reward structure are based on the theories of truthinducing logarithmic scoring for non-zero-sum, non-cooperative games. They are beyond the scope of this article but contained in Prelec [60]. The novel aspect of the scoring system is that the IP rewards participants for the quality of the questions that they contribute to the exercise. A “good” question, according to the scoring system, satisfies two criteria. First, it identifies something distinctive and descriptive about the concept presented. Second, it is a new contribution to the discussion about this particular concept. Questions that merely reformulate information contained in earlier items will not be rewarded. As the game progresses the list of statements grows – each statement adds a new and different perspective on the concept. Encoders have strong incentives to express needs clearly, potentially making the IP effective at eliciting difficult-to-articulate needs and identifying respondents who are skilled at doing so. Decoders have strong incentives to answer truthfully about their perceptions of the product, thus making the IP an interesting new way to elicit respondents’ true perceptions of concepts. The IP has been pilot tested with concept cars and visual advertising materials and has been benchmarked against a control procedure, which has the same “look and feel” as the information pump, but without the interactive scoring system. Early indications suggest that the IP provides customer statements that independent judges evaluate as more creative [60]. Currently, the IP is limited by its need for respondents to play the game simultaneously, however, work is underway to develop an asynchronous version in which respondents can visit a secure website at their own convenience over the course of a study. THE VIRTUAL CUSTOMER PAGE 23 Virtual Customer Discussion Web-based interviewing is a relatively new development that has the potential to transform the way PD teams gather information from and interact with customers. It relies on advances in communication, conceptualization, and computation that increase the effectiveness and efficiency of linking the voice of the customer directly to the capabilities of the PD team. However, there are many challenges to overcome. Like other disruptive technologies, the initial applications may not perform as well on traditional measures as do existing methodologies [3, 10]. Initially, PD teams will have to make tradeoffs; the old and the new will co-exist, with each being used for its unique advantages. However, as more researchers and more firms evolve webbased customer input methods, we expect the weaknesses to be overcome and the strengths to improve. We expect web-based interviewing soon to become an important paradigm for fulfilling many of the customer-input requirements of the PD team. While virtual customer methods may be used at every stage of product development, not every method will be used at every stage. Figure 17 is based on our early experiences and is one example of how the six methods might be used synergistically throughout the PD process. The “PD funnel” in the center of Figure 17 is an abstract representation of the stages of PD as products move from ideas, to concepts, to design & engineering, to testing, and to launch. The ovals in the funnel represent products that are winnowed, refined, and improved at each stage based on customer input and other analyses. The four groups of products separated by dotted lines abstract the concept of parallel development and product-platform development. For simplicity, Figure 17 has the look and feel of a stage-gate process, but the applicability of virtual customer methods is equally as strong for the new spiral PD processes. The IP’s strength is its ability to gather the language of the customer, including features and needs that are difficult for customers to articulate. One use is to identify opportunities and ideas and to focus engineering teams on customer needs as seen through the lens of the customers’ language. Similarly, FP can be applied early in the PD process. Its strength is the ability to screen large numbers of potential product features quickly. Because reasonable estimates can be obtained with fewer questions than there are unknown parameters, the PD team can trade off a small amount of accuracy for the ability to direct design attention toward a small, highleverage set of product features. THE VIRTUAL CUSTOMER PAGE 24 As the product moves from concept generation to design & engineering, the PD team needs more accuracy and a deeper understanding of the tradeoffs that customers make when evaluating products. Here WCA shines. The methods are built upon over twenty years of conjoint-analysis research and application. The new interfaces rely on proven estimation methods while bringing advanced conceptualization to virtual features so that they might be tested earlier in the process and with greater speed. UD complements conjoint analysis by providing a means by which customers design their own products. UD is particularly suited to products where the features interact and where a conjoint-analysis application would need a large, complex experimental design to estimate the interactions. In such situations, the PD team might be willing to sacrifice the ability to measure detailed feature importances for each respondent. UD is also suited to instances where customers need to learn their own preferences for really new products, and might even be used as a training step prior to WCA or FP. Once fully integrated product concepts are “developed,” they need to be tested. Here the web brings a greater ability to evaluate multiple virtual concepts quickly. VCT enables the PD team to get rapid and inexpensive feedback on the Product (with a big P) that includes descriptions of the product and its features, illustrations of the product in use, and marketing elements such as brochures, magazine articles, advertisements, and simulated word of mouth. In the early 1990s, virtual Product testing relied on expensive clinics in which customers were brought to a central location and shown video tapes and other media [55, 58, 65, 79]. Such clinics often cost hundreds of thousands of dollars. In the mid 1990s, virtual Product testing moved to computerbased methods called information acceleration. However these, too, were expensive and difficult to implement [78, 81]. As web access and web panels improve, web-based VCT promises to reduce these costs dramatically and to reduce time delays from weeks (or months) to days. New software tools are making development less expensive, broadband communications are making it feasible to stream multimedia experiences to customers, and pre-recruited panels (for consumer goods) are making it quick. STOC provides an alternative concept screening method, especially when the PD team is dealing with a product in which customers’ preferences might depend upon what other customers prefer (e.g., a fashion watch or personal communication device). However, while STOC provides reliable estimates, it is too early to tell whether STOC will realize the external validity of more proven concept-testing methods. THE VIRTUAL CUSTOMER PAGE 25 The six virtual customer techniques reviewed in this article are just of sampling of themethods that will evolve as information and communication technologies advance. For example,Urban [75] is experimenting with virtual engineers that can “listen in” to customers as theysearch the web for products to buy. His early work with truck purchasing is promising.What is clear, however, is that the new information and communications technologies areexpanding the efficient frontier of the accuracy vs. cost/time tradeoff. In many situations, web-based methods are cost efficient and their lower entry barriers put their capabilities directly intothe hands of the PD team. A day might come when conducting virtual customer tests is almostas common as performing “what if” analyses with spreadsheet software.Besides bringing more customer input to the PD process, virtual customer methods mightencourage a greater number of concepts to be explored and tested with customers. Srinivasan,Lovejoy, and Beach [71] suggest further that PD teams will undertake more parallel concept test-ing prior to “freezing” the design of a new product. Dahan and Mendelson [18] quantify the ar-gument and suggest that under certain distributions of profit uncertainty, the optimal number ofconcepts to be explored grows dramatically as (1) the cost per test declines and (2) when the up-side profit opportunity declines at a slower-than-exponential (i.e., “fat-upper-tailed”) manner.Current virtual customer methods have their weaknesses. They rely on virtual prototypesrather than physical prototypes; software development is still embryonic, often requiring customprogramming for each application; panels are still being developed and their representativenessis still being tested; and experience with the methods pales compared to experience with tradi-tional methods. Initial tests suggest high face validity and good internal validity, but only WCAand FP have been subjected to tests of external validity. Nonetheless, we are optimistic thatthese challenges will be overcome by the product-development community and that virtual cus-tomer methods will emerge as an integral component in the practice of product development. THE VIRTUAL CUSTOMER, REFERENCESPAGE R1