The conventional wisdom is that people who play a lot of sports have more sexual partners than those who do not. To test this, a group of French researchers asked two groups of students how many sex partners they had 1056 had in the previous year (Faurie et al. 2004). One group was composed of 250 physical education majors who regularly participated in sports; the other group was composed of 50 biology majors who did not regularly do sports. The distribution of number of sex partners is shown in the graph below. Biology majors claimed an average of 1.24 sex partners in the previous year, while sports majors claimed an average of 2.4 partners in the previous year.

As you can see, the distributions are very different from a normal distribution, and even with a log transformation the distributions are not normal. As a result, the researchers used a Mann–Whitney U-test to compare the median numbers of sex partners for the two groups. They 1059 found that the U₁ value corresponding to the biology majors was 8500.5, while the U₂ value corresponding to the sports group was 3999.5.

a. Finish the Mann–Whitney U-test for them. State the hypotheses and reach a conclusion.

b. Comment on your results in light of the assumptions of the Mann– Whitney U-test.

Transcribed Image Text:

Percent Percent 50 40 30 20 10- 0 50 40 30 20- 10- 0 0 Sports students Biology students 10 20 Number of sex partners 30