RUI: Collaborative Research: Sample Size Bias in Judgments of Averages

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This project focuses on a phenomenon of quantitative cognition called sample size bias, which occurs when people make judgments of averages. Specifically, as the number of items in a set increases, people judge the average to be greater. For example, the average of a set of ten numbers is judged to be greater than the average of five numbers -- even when the two sets have the same average. But sample size bias also occurs for conceptual dimensions such as risk. For example, the average heart-attack risk of ten people is judged to be greater than the average heart-attack risk of five people. The core of this project is a series of empirical studies in which a cross-section of people judge several kinds of averages under a variety of conditions. These studies have two purposes. The first is to test a theory that assumes that set size automatically activates an analog representation of magnitude in the brain, which in turn affects the representation and judgment of the average. The second is to see whether the sample size bias affects other kinds of judgments about averages, including judgments about one's own experience and behavior.This work is important for a number of reasons. First, the theory being tested has the potential to help integrate sample size bias with similar phenomena from distinct areas of research including judgment and decision making, perception, and the neuroscience of quantitative cognition. Second, this research will help identify real-world contexts in which people's judgments of averages are likely to reflect sample size bias. For example, surveys often ask people to make judgments about what is average or typical for them or their peers (e.g., the average number of times they use health services per year). It is important to know whether such judgments are likely to be systematically biased and how such biases might be corrected. Finally, this project will provide high quality research training and experience to a diverse group of undergraduate and master's-level students at California State University, Fresno and Appalachian State University. This in turn will prepare them to succeed in doctoral studies in any of a variety of areas, cognitive and social psychology, judgment and decision making, and management science.