Consider the bond stress strength data from the portland cement formulation experiment. construct a 95% confidence interval for the difference in means. M1 <-c (16.85, 16.40, 17.21, 16.35, 16.52, 17.04, 16.96, 17.15, 16.57) M2 <-c (17.50, 17.63, 18.25, 18.00, 17.86, 17.75, 18.22, 17.96, 18.15)
t.test(M1, M2, conf.level = 0.95)