Estimating the Optimal Number of Alternatives to Be Explored in Large Design Spaces: a Step towards Incorporating Decision Making Cost in Design Decision Models

Exploration of design spaces is an important step in decision-based design. In consumer product development, precise design specifications are not known at the beginning of the design process. It is usually design team’s responsibility to find out the specifications as a part of the design process. This results in large design spaces in consumer product development. Furthermore, market window is usually limited. Thus, it is impractical to examine all possible design alternatives. As part of the design process, design teams need to determine how many alternatives to examine and how much evaluation time should be devoted to examining each alternative. This paper presents a model for estimating the optimal number of alternatives to be explored and the optimal evaluation time for each alternative by incorporating cost of decision-making in the overall design decision model. We also describe a design case study and investigate how characteristics of design task parameters influence the optimal number of alternatives and the optimal evaluation time. Our results indicate that it is difficult to intuitively identify the optimal values of the number of alternatives and the evaluation time for even very simple design tasks. We describe the practical issues that need to be addressed to make these decisions and discuss how the model proposed in this paper can be extended to handle more general cases of design tasks.