Ethnicity and pain perception. An investigation of ethnic differences in reports of pain perception was presented at the annual meeting of the American Psychosomatic Society (Mar. 2001). A sample of 55 blacks and 159 whites participated in the study. Subjects rated (on a 13-point scale) the intensity and unpleasantness of pain felt when a bag of ice was placed on their foreheads for two minutes.

(Higher ratings correspond to higher pain intensity.)

A summary of the results is provided in the following table.

Blacks Whites Sample size 55 159 Mean pain intensity 8.2 6.9

a. Why is it dangerous to draw a statistical inference from the summarized data? Explain. LO5

b. Give values of the missing sample standard deviations that would lead you to conclude (at a = .05) that blacks, on average, have a higher pain intensity rating than whites.

c. Give values of the missing sample standard deviations that would lead you to an inconclusive decision (at a = .05) regarding whether blacks or whites have a higher mean intensity rating.