Beliefs underlying random sampling.

In Experiment 1, subjects estimated {1) the mean of a random sample of 10 scores consisting of 9 unknown scores and 1 known score that was divergent from the population mean and {2} the mean of the 9 unknown scores. The modal answer {about 40% of the responses} for both sample means was the population mean. The results extend the work of Tversky and Kahneman {1971} by demonstrating that subjects hold a passive, descriptive view of random sampling rather than an active-balancing model. This result was explored further in in-depth interviews {Experiment 2}, wherein subjects solved the problem while explaining their reasoning. The interview data replicated Experiment 1 and further showed: {1} that subjects’ solutions were fairly stable--when presented with alternative solutions, including the correct one, few subjects changed their answers; !2} little evidence of a balancing mechanism; and {3} that acceptance of both means as 400 is largely a result of the perceived unpredictability of "random samples."