Preferred Name

Derek C.Sauder

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Date of Graduation

Spring 2017

Document Type


Degree Name

Master of Arts (MA)


Department of Graduate Psychology


Christine DeMars

Allison Ames Boykin

S. Jeanne Horst


Researchers utilizing either experimental or quasi-experimental research often want to compare group means. However, with more than two groups, comparing group means may result in an inflated Type I error rate, the probability of wrongly rejecting a null hypothesis. Researchers often employ analysis of variance (ANOVA) methodology to compare more than two group means. Post-hoc comparison procedures (PCPs) are utilized to indicate which group means differ following a significant ANOVA. SPSS provides 18 options for PCPs. The purpose of this study was to determine which PCP provides the best power while maintaining Type I error control when assumptions of ANOVA are met and when they are not met. Data were simulated in a variety of conditions to address this issue. Only those tests designed for assumption violations, Dunnett’s C, Dunnett’s T3, Games-Howell, and Tamhane, adequately controlled Type I error in all conditions. Power results were similar for all four tests, with the Games-Howell being slightly higher than the other four tests. I recommend using the Games-Howell procedure unless extenuating circumstances exist.



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