Discusses various heuristics and biases employed in subjective assessment of uncertainty. In increasingly more types of analyses of problems there is need to express uncertainty in probabilistic terms. Such questions as: What will the foreign oil price be in 1985? or What is the current availability of domestic natural gas? if expressed in probabilistic terms, can be an aid to informed decisionmaking. The paper focuses on the cognitive influences of availability, anchoring, and representativeness and how these influences commonly distort one's assessment of uncertainty in probabilistic terms, and briefly how such influences can be avoided. A questionnaire was given to 36 RAND researchers. Almanac questions such as — What was the population of Cairo in 1966? — among others, were asked in order to determine if experienced researchers who deal in problems of uncertain future events exhibit the same biases as others of various backgrounds, which have been studied elsewhere, when thinking intuitively.
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