A measure of effect size for experimental designs with heterogeneous variances.
A recent trend in the psychological literature has been to include measures of effect size when reporting probability values. The several measures of effect size associated with the Student t test for two independent samples are appropriate only when the variances are homogeneous. In this paper, commonly used measures of effect size are considered and compared, using four data sets. A chance-corrected measure of effect size is provided for two or more treatment groups characterized by either homogeneous or heterogeneous variances.
Johnston
Janis F
JF
Department of Sociology, Colorado State University, Fort Collins, CO 80523-1784, USA. janisj@lamar.colostate.edu
Berry
Kenneth J
KJ
Mielke
Paul W
PW
D015987:Effect Modifier, Epidemiologic; D006801:Humans; D008960:Models, Psychological; D012107:Research Design