Suppose that four normal populations have common variance 2 = 25 and means 1 = 50, 2

Suppose that four normal populations have common variance μ2 = 25 and means μ1 = 50, μ2 = 60, μ3 = 50, and μ4 = 60. How many observations should be taken on each population so that the probability of rejecting the hypothesis of equality of means is at least 0.90? Use a = 0.05.