In a pilot study with groups P, Q, R, S each with n = 6, the ANOVA indicates a significant overall F. MSE = 5.0, group means are P = 10, Q = 12, R = 16, S = 23. Degrees of freedom for error is 24, and the studentized range critical value for k = 4 and df = 24 at alpha = 0.05 is qcrit = 4.03. Calculate which pairwise comparisons are significant.

• A. All pairwise comparisons are significant except P vs Q (only P vs Q fails to exceed qcrit).
• B. Only adjacent-mean comparisons (P vs Q, Q vs R, R vs S) could possibly be significant, while extremes (P vs S) are ignored by the studentized range adjustment.
• C. Only P vs S and Q vs S are significant, because differences involving the largest mean always dominate in Tukey tests regardless of MSE.
• D. No pairwise comparisons are significant because the ANOVA is significant only for the global F and does not imply any pairwise difference will be significant under Tukey.

Answer: (A)