11.44 AIDS and condom use Chatterjee et al. (1995, p. 132)

described a study about the effect of condoms in reducing the spread of AIDS. This two-year Italian study followed heterosexual couples where one partner was infected with the HIV virus. Of 171 couples who always used condoms, 3 partners became infected with HIV, whereas of 55 couples who did not always use condoms, 8 partners became infected. Test whether the rates are significantly different.

a. Define p1 and p2 in this context and specify the null and two-sided alternative hypotheses.

b. For these data, software reports Pearson Chi-Square = 14.704, DF = 1, P-Value = 0.0001

*Note* 1 cell with expected count less than 5 Fisher’s exact test:

P-Value = 0.0007 Report the result of the test that you feel is most appropriate for these data. For the test you chose, report the P-value and interpret in the context of this study.