EXAMPLE 8.11 Sample Sizes for Preferences of Women and Men

Refer to Example 8.10, where we used the margin of error to find the sample sizes for comparing the preferences of women and men for two commercials. Let's find the sample sizes required for a significance test that the two proportions who prefer Commercial A are equal () using a two-sided alternative with and , , and 80% (0.80) power. Outputs from JMP and Minitab are given in Figure 8.8. We need women and men for our study.