Judged frequency of lethal events.

A series of experiments studied how people judge the frequency of death from various causes.The judgments exhibited a highly consistent but systematically biased subjective scale of frequency.Two kinds of bias were identified: (a) a tendency to overestimate small frequencies and underestimate larger ones, and (b) a tendency to exaggerate the frequency of some specific causes and to underestimate the frequency of others, at any given level of objective frequency.These biases were traced to a number of possible sources, including disproportionate exposure, memorability, or imaginability of various events.Subjects were unable to correct for these sources of bias when specifically instructed to avoid them.Comparisons with previous laboratory studies are discussed, along with methods for improving frequency judgments and the implications of the present findings for the management of societal hazards.How well can people estimate the fre-how small a difference in frequency can be quencies of the lethal events they may en-reliably detected?Do people have a concounter in life (e.g., accidents, diseases, sistent internal scale of frequency for such homicides, suicides, etc.) ?More specifically, events?What factors, besides actual frequency, influence people's judgments?The answers to these questions may have to society.Citizens must Defense and was monitored by the Office of Naval assess rlsks accurately in order to mobilize Research under Contracts N00014-76-C-0074 and society's resources effectively for reducing N00074-78-C-0100 (ARPA Order Nos.3052 and hazards and treating their victims.Official ,5469) under subcontract to Oregon Research Inreco nition of the irn p 0r t a nce of valid risk stitute and Subcontracts 76-030-0714 and 78-072-b ., ,.,<<.,• ^ » 0722 to Perceptronics, Inc. from Decisions and assessments is found m the vital statistics Designs, Inc. that are carefully tabulated and periodically We would like to thank Nancy Collins and reported to the public (see Figure 1 ).There Peggy Roecker for extraordinary diligence and ; Sj i lowev er, no guarantee that these statispatience in typing and data analysis.We are also .