On effect size.

Abstract

The call for researchers to report and interpret effect sizes and their corresponding confidence intervals has never been stronger. However, there is confusion in the literature on the definition of effect size, and consequently the term is used inconsistently. We propose a definition for effect size, discuss 3 facets of effect size (dimension, measure/index, and value), outline 10 corollaries that follow from our definition, and review ideal qualities of effect sizes. Our definition of effect size is general and subsumes many existing definitions of effect size. We define effect size as a quantitative reflection of the magnitude of some phenomenon that is used for the purpose of addressing a question of interest. Our definition of effect size is purposely more inclusive than the way many have defined and conceptualized effect size, and it is unique with regard to linking effect size to a question of interest. Additionally, we review some important developments in the effect size literature and discuss the importance of accompanying an effect size with an interval estimate that acknowledges the uncertainty with which the population value of the effect size has been estimated. We hope that this article will facilitate discussion and improve the practice of reporting and interpreting effect sizes.

Adaptação e evidências de validade da Bateria de Personalidade Prosocial no Brasil

“…Também não foram identificados estudos específicos de adaptação para outras culturas, mas a BPP tem sido utilizada em estudos realizados em diferentes países (Finkelstein, Penner & Brannick, 2005;Kulik, 2007;Penner & Finkelstein, 1998;Perugini & cols., 2011;Rabelo & cols., 2012). Cabe ainda apontar que a despeito de tais evidências, a BPP, por ser um instrumento de autorrelato, apresenta os problemas inerentes a esse tipo de medida (Nisbett & Wilson, 1977;Nosek, Hawkins & Frazier, 2011;Paulhus, 1984), além de problemas de análise estatística, como a excessiva valorização por parte dos pesquisadores da área de correlações e predições estatisticamente significativas em detrimento, por exemplo, da avaliação dos tamanhos de efeito envolvidos em tais relações (Cohen, 1994;Kelley & Preacher, 2012;Wagenmakers, Wetzels, Borsboom, van der Maas & Maas, 2011).…”

“…Considerando o tamanho das nossas amostras, a probabilidade de se identificar alguma relação que atinja a significância é maior, embora tais diferenças não sejam necessariamente relevantes (Cohen, 1994;Wagenmakers & cols., 2011), e os dados relacionados com o tamanho de efeito apresentados aqui indicam que as diferenças não são robustas. A comparação, nesse aspecto, com estudos anteriores é comprometida pela ausência de relato do tamanho de efeito (Sampaio & Menezes, 2011), algo ainda comum na psicologia (Kelley & Preacher, 2012).…”

Do urban environments increase the risk of anxiety, depression and psychosis? An epidemiological study

“…In large sample sizes such as in the present study, even trivially small effects can be statistically significant, therefore, it is necessary to consider the magnitude of the observed effect and whether it represents an effect that is likely to be of practical significance. Although what constitutes an effect size of a magnitude indicating a potentially important effect in different fields is somewhat subjective and will depend on the specific research area (Kelley & Preacher, 2012), we would argue that this size of effect is, in the context of epidemiological research large enough to be considered potentially important. For example, many epidemiological associations which are considered to be important have shown beta coefficients smaller than this, such as the association between smoking and cognitive decline in older adulthood (Anstey et al, 2007).…”

Dimensions of Decision-Making Process Quality and Company Performance: A Study of Top Managers in Slovenia

“…We also calculated the effect size with the Cohen's d coefficient, which calculates the overlapping of the values of the control and the research group. Effect size is a quantitative measure of the strength of a phenomenon (Kelley & Preacher, 2012). The effect sizes according to the Cohen's d coefficient are when the absolute value of the coefficient is the following: very small -0.01; small -0.2; medium 0.5; large 0.8; very large 1.2; and huge 2.0 (Cohen, 1988;Cohen, 1992;Sawilowsky, 2009).…”