Document Type


Degree Name

Master of Arts (MA)




Faculty of Science

First Advisor

Robert Gebotys

Advisor Role

Thesis Supervisor


The use of intuitive heuristics has been put forward as an explanation for people’s assessment of probabilities (Kahneman & Tversky, 1972, 1973; Tversky & Kahneman, 1971, 1974). This phenomenon is seen as robust since “experts” (professional psychologists) make use of the same heuristics as “novices” (laypeople), despite having “had extensive training in statistics” (Tversky & Kahneman, 1974, p. 1130). However, replacing probability calculus with heuristics can lead to systematic errors and biases in probabilistic judgments. This study was designed to investigate the effects of statistical training on how people think about probabilistic judgments. Subjects’ knowledge base of probabilistic concepts, as defined by the number of correct answers on the Probability Knowledge Questionnaire, was assessed prior to receiving (or not) a brief training session. Immediately following training, subjects completed a Probability Test which consisted of ten Tversky and Kahneman (e.g., 1974) problems. The findings suggested that the training served to make a statistical approach to the probability test problems more salient. It was also observed that “novices”, with training, correctly solved a significantly higher proportion of test problems than did “experts” with no training. Finally, training served to increase subjects’ judgmental accuracy as measured by confidence ratings. The training session, which was designed to sensitize subjects to some basic probabilistic concepts, was successful in reducing the use of heuristics. Information on why people use heuristics and their robustness appears to point to a minimal probability knowledge base.

Convocation Year


Convocation Season