Consider iid random variables X1...Xn of mothers' ages in years arising from a population with mean u1 and variables σ2[1].
Corresponding to Xi, is the age Yi in years of the mother's eldest child. The ages of eldest children who have mothers that are still alive arise from the distribution with mean u2 and variables σ2[2]. There is interest in testing Ho: u1-u2=20 versus H1: u1- u2 > 20. Approximately how large should n be such that the power of the test is 0.90 When u1-u2=25 years?