Which statement correctly describes the MSE from ANOVA and its use in pairwise t-tests?

• A. MSE is the total sample variance ignoring group membership and is used only when groups have very different variances; otherwise you use the smaller of the group variances for pooling.
• B. MSE is the mean squared error (within-group variance) pooled across groups and is used as the common variance estimate in pairwise t-tests because it reflects typical variation of observations around their group means.
• C. MSE is the mean squared estimate of the grand mean's error and should be replaced by the median absolute deviation in all Bonferroni calculations because medians are robust to outliers.
• D. MSE is the between-group mean square that measures differences among group means and is therefore used in pairwise tests to inflate the denominator and discourage rejections.

Answer: (B)