The Status of Multiple Comparisons: Simultaneous Estimation of all Pairwise Comparisons in One-Way ANOVA Designs

Abstract

Recent work, spearheaded by Charles Dunnett (1980a), leads to the conclusion that the Tukey-Kramer (TK) method (popularly known as “Kramer's Method”) is the recommended multiple comparisons procedure for the simultaneous estimation of all pairwise differences of means in an imbalanced one-way ANOVA design with homogeneous variances. Nine other multiple comparisons methods are compared to each other and to the TK method using the criteria of conservativeness, narrowness of confidence intervals, robustness, and ease of use. The degree of superiority of the TK method over these methods, especially over the popular Bonferroni method, is sufficient to warrant recommending its use. Because of the lack of robustness of the TK method in heterogeneous variance cases, other methods are recommended.

Key Words:

• Bonferroni methods
• Kramer method
• Kramer method
• Simultaneous pairwise estimation of means
• Tukey method