A researcher has 6 groups with 6 observations in each group. To look up the Tukey q critical value for alpha = 0.05, what degrees of freedom should they use from the ANOVA?

• A. df = 35 (using total observations minus 1, which is incorrect for a Tukey q lookup because it ignores the group count)
• B. df = 36 (using the total number of observations directly, which would be appropriate for some other tables but not the studentized range since you must subtract the number of groups)
• C. df = 30
• D. df = 24 (computed by subtracting 12 because 6 groups × 2 degrees per group are removed in this unusual method which mistakenly double-subtracts group contributions)

Answer: (C)