Generalized eta squared for multiple comparisons on between-groups designs
Psicotema
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How to Cite

Trigo Sánchez, M. E., & Martínez Cervantes, R. J. (2016). Generalized eta squared for multiple comparisons on between-groups designs. Psicothema, 28(Número 3), 340–345. Retrieved from https://reunido.uniovi.es/index.php/PST/article/view/11300

Abstract

Background: Psychological and educational researchers are experiencing many practical difficulties in following the guidelines of the American Psychological Association (APA) for their statistical analyses: one such difficulty is the reporting of an effect-size measure along with each test of statistical significance (APA, 2010). The problem is exacerbated when researchers focus on contrast analysis instead of omnibus tests and when the Type-I error rate per comparison has to be adjusted. Method: Several reasons for this problem are discussed, with emphasis on the facts that researchers may be presented with too many optional effect-size measures with varying degrees of adequacy in several designs, and common statistical packages fail to provide appropriate effect-size measures for contrast analysis. Results: This study proposes specific procedures (also implemented in spreadsheets) to compute generalized eta squared for various kinds of hypotheses, either general or specific, for one-factor and factorial between-group designs, and with manipulated and/or measured factors. Conclusions: Finally, conclusions are drawn concerning the need to take into account the kind of design and the kind of hypothesis in order to calculate comparable effect-size indexes across different types of studies and to prevent an overestimation of effect size.
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