Two samples of sizes n1 = 20 and n2 = 15 taken from two independent normal populations with known standard deviations, σ1 = 3.5 and σ2 = 4.2, produced sample averages, x¯1 = 15.5 and x¯2 = 13.8. At the α = 0.05 signi?cance level, test the null hypothesis that the means are equal against the alternative that they are not. Interpret the result. Repeat this test for Ha : μ1 > μ2 ; interpret the result.