Testing for Constant Difference To test the null hypothesis that the difference between two population proportions is equal to a nonzero constant

c, use the test statistic As long as n1 and n2 are both large, the sampling distribution of the test statistic z will be approximately the standard normal distribution. Refer to Exercise 26 and use a 0.05 significance level to test the claim that the headache rate of Viagra users is 10 percentage points more than the percentage for those who are given a placebo.