In many high-fertility countries, and especially in sub-Saharan Africa, substantial proportions of women give non-numeric responses when asked about desired family size. Demographic transition theory has interpreted responses of "don't know" or "up to God" as evidence of fatalistic attitudes toward childbearing. Alternatively, these responses can be understood as meaningful reactions to uncerta...

This paper introduces the concept of a random variable, which is nothing more than a variable whose numeric value is determined by the outcome of an experiment. To describe the probabilities that are associated with these numeric values in a concise and conceptually useful manner, the probability distribution and probability density function are introduced. Then, the moment generating function ...

Two-dimensional (2D) turbulence in the energy range exhibits nonuniversal features, manifested in the departure (at low k) from the k(-5/3) energy spectrum law, variable energy flux, and irregular, nonlocal transfers. To unravel the underlying mechanism we conducted a detailed study of the 2D turbulence in spectral and physical space. It revealed complex multiscale organization of vorticity fie...

Many claims are being made about the advantages of conducting surveys on the Web. However, there has been little research on the effects of format or design on the levels of unit and item response or on data quality. In a study conducted at the University of Michigan, a number of experiments were added to a survey of the student population to assess the impact of design features on resulting da...

When people estimate a numeric value after judging whether it is larger or smaller than a high or low anchor value (comparative question), estimates are biased in the direction of the anchor. One explanation for this anchoring effect is that people selectively access knowledge consistent with the anchor value as part of a positive test strategy. Two studies (total N = 184) supported the alterna...

People often estimate the average duration of several events (e.g., on average, how long does it take to drive from one's home to his or her office). While there is a great deal of research investigating estimates of duration for a single event, few studies have examined estimates when people must average across numerous stimuli or events. The current studies were designed to fill this gap by e...

In general, no disproportionate detrimental effects of irrelevant background speech on cognition are found in aging individuals, although this is predicted by the inhibitory view of aging. This may be due to the nature of the primary task (most studies involve a verbal learning task) or the cognitive level at which irrelevant speech interferes with this task. In this study, the irrelevant speec...