Assessing small non-zero perceptions of chance: The case of H1N1 (swine) flu risks
- 222 Downloads
Feelings of invulnerability, seen in judgments of 0% risk, can reflect misunderstandings of risk and risk behaviors, suggesting increased need for risk communication. However, judgments of 0% risk may be given by individuals who feel invulnerable, and by individuals who are rounding from small non-zero probabilities. We examined the effect of allowing participants to give more precise responses in the 0–1% range on the validity of reported probability judgments. Participants assessed probabilities for getting H1N1 influenza and dying from it conditional on infection, using a 0–100% visual linear scale. Those responding in the 0–1% range received a follow-up question with more options in that range. This two-step procedure reduced the use of 0% and increased the resolution of responses in the 0–1% range. Moreover, revised probability responses improved predictions of attitudes and self-reported behaviors. Hence, our two-step procedure allows for more precise and more valid measurement of perceived invulnerability.
KeywordsRisk perceptions Expectations Visual linear scale Magnifier scale H1N1 flu
JEL ClassificationI10 D84 C83
This work was supported by the National Institute of Aging [grant #R01AG20717] as well as the Center for the Advancement of Microbial Risk Assessment [EPA Star grant #R83236201], and benefited from support and comments by Courtney Gidengil, Tania Gutsche, Katherine Harris, Arie Kapteyn, Jeanne Ringel, Kip Viscusi, Bas Weerman, and an anonymous reviewer.
- Bruine de Bruin, W., & Carman, K.G. (in press). Measuring risk perceptions: What does the excessive use of 50% mean? Medical Decision Making. Google Scholar
- Lillard, L. A., & Willis, R. (2001). Cognition and wealth: The importance of probabilistic thinking. Michigan Retirement Research Center Working Paper UM00-04.Google Scholar
- Siegel, S., & Castellan, N. J., Jr. (1988). Nonparametric statistics for the behavioral sciences (2nd ed.). Boston: McGraw-Hill.Google Scholar