Public perceptions of health risks. The Journal of Experimental Psychology: Learning, Memo...

Public perceptions of health risks. The Journal of Experimental Psychology: Learning, Memory, and Cognition (July 2005) published a study of the ability of people to judge the risk of an infectious disease. The researchers asked German college students to estimate the number of people infected with a certain disease in a typical year. The median estimates, as well as the actual incidence for each in a sample of 24 infections, are reproduced in the accompanying table and saved in the INFECTION file.

a. Use graphs to demonstrate that the variables Actual incidence and Estimated incidence are not normally distributed.

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b. Recall that the researchers used regression to model the relationship between Actual incidence and Estimated incidence. How does the result you found in part a affect this analysis?

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c. Find Spearman’s correlation coefficient for the two variables. Interpret this value.

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d. Refer to part c. At α =.01 , is there a positive association between Actual incidence and Estimated incidence?

Based on Hertwig, R., Pachur, T., and Kurzenhauser, S. “Judgments of risk frequencies: Tests of possible cognitive mechanisms.” Journal of Experimental Psychology: Learning, Memory, and Cognition , Vol. 31, No. 4, July 2005.