Exercise 12.7.4 contained data on stress measurements for four different types of rubber. Four observations were taken on each type of rubber; the means are repeated below,

Material A B C D Mean 26.4425 26.0225 23.5325 29.9600 and the sample variance of the 16 observations is 14.730793. Test for differences between all pairs of materials using α = 0.05 for the LSD, Bonferroni, and Tukey methods. Give 95% confidence intervals for the differences between all pairs of materials using the BSD method.