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Please use this identifier to cite or link to this item: https://hdl.handle.net/2445/218943
How to proceed when both normality and sphericity are violated in the repeated measures ANOVA
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Adjusted F-tests have typically been proposed as an alternative to the F-statistic in repeated measures ANOVA. Despite considerable research, it remains unclear how these statistics perform under simultaneous violation of normality and sphericity. Accordingly, our aim here was to conduct a detailed examination of Type I error and power of the F-statistic and the Greenhouse-Geisser (F-GG) and Huynh-Feldt (F-HF) adjustments, manipulating the number of repeated measures (3-6), sample size (10-300), sphericity (epsilon estimator of Greenhouse-Geisser from its lower to upper limit), and distribution shape (slight to extreme deviations from normality). The findings show that the behavior of F-GG and F-HF depends on the degree of violation of both normality, sphericity, and sample size. Overall, we suggest using F-GG under violation of sphericity and slight or moderate deviations from normality in all sample size; with severe deviations from both normality and sphericity F-GG may be used with a sample size larger than 10; and with extreme deviation from both normality and sphericity this statistic may be used with a sample size larger than 30. In the event of discrepant results between F-GG and F-HF, the choice depends on the epsilon value.
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BLANCA MENA, M. José, et al. How to proceed when both normality and sphericity are violated in the repeated measures ANOVA. Anales de Psicología. 2024. Vol. 40, num. 3, pags. 466-480. ISSN 0212-9728. [consulted: 7 of August of 2026]. Available at: https://hdl.handle.net/2445/218943