Judged frequency of lethal events.

Abstract

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 In-reco nition of the irn p 0r t a nce of valid risk . , ,.,<<., • ^ » 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 .

Are mature smokers misinformed?

“…Some have questioned whether individuals are even be able to form probabilities (see, e.g., Hanson and Kysar 2001), while others point to sensitivity of responses to the framing of the questions (e.g., Tversky and Kahneman 1981). There is evidence that people overpredict very low and underpredict very high probability events (e.g., Lichtenstein, et al 1987 andSlovic 2000). In addition, there is evidence that people overweight changes in probabilities when they change from values near zero or one.…”

Gestão e avaliação de risco em saúde ambiental

“…Implica elevada incerteza (probabilidade) que, entre outros conceitos, varia enormemente, de acordo com o grau de importância dado pelo público (em geral, via órgãos formadores de opinião) ao fenômeno ou evento. Morgan & Henrion (1992), redesenhando o gráfico elaborado por Lichtenstein et al (1978) (Gráfico 7), observaram que a heurística, mesmo operacionalizada junto a uma população mais esclarecida, estabelece resultados bastante tendenciosos (enviesados), fora da realidade dos fatos. Os casos de botulismo, por exemplo, estariam sendo superestimados pela população entrevistada, ao passo que os derrames cerebrais, subestimados.…”

How Representations of Knowledge Shape Actions

“…Studies of frequency and probability assessments, however, commonly report overestimation of rare events (Hertwig, Pachur, & Kurzenhäuser, 2005 ;Lichtenstein et al, 1978 ). Moreover, studies recording people's estimates of rare events in the sampling paradigm found them to be well calibrated or a little too high relative to the experienced frequency (Hau et al, 2008 ;Ungemach et al, 2009 ).…”