Subjective sampling distributions and the additivity of estimates

Abstract.— Previous studies of sampling distributions have been conducted almost exclusively under the assumption that persons behave in accordance with the “fundamental convention” of probability, i.e. that the sum of all probability estimates will equal 1. When this assumption was tested by asking subjects to give “unrestricted” probability estimates of all possible outcomes of samples from a given population, a general tendency of overestimation made the sum of all probabilities exceed 1 to a considerable extent. The subjective sampling distributions appeared to be unaffected by sample size (N=5 or 10) and number of outcomes, and were flatter than the corresponding “objective” sampling distributions.