Pollatsek et al. (1984)

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 inter- view 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 sample."