help sizefx

Title

sizefx -- Calculate Cohen's d, Hedges' g, and the effect size (ES) correlation (r)

Syntax

sizefx varlist [if] [in]

Description

sizefx computes Cohen's d, Hedges' g, and effect size (ES) correlations (r) for the two variables specified in varlist. The two variables specified correspond to the variables in a ttest, although the "==" operator is not used in the sizefx syntax.

The command displays Cohen's d statistic (Cohen 1988) using the pooled variance of the variables and Hedges' g statistic. The pooled variance for an unpaired t-test is used to calculate effect size even when using a dependent sample or correlated designs (Dunlap et al. 1996).

Additionally, it displays the effect size (ES) correlation (r) using the value of Cohen's d.

Examples

. sizefx age1 age2
. sizefx before after

References

Cohen, J. (1988) Statistical power analysis for the behavioral sciences, 2nd ed. Hillsdale, NJ: Lawrence Earlbaum Associates.

Dunlap, William P., Cortina, Jose M., Vaslow, Joel B., and Burke,
Michael J. (1996) Meta-analysis of experiments with matched
groups or repeated measures designs. Psychological Methods 1
no. 2, 170-177.

Thalheimer, W., and Cook, S. (2002, August) How to calculate effect sizes from published research articles: A simplified methodology. Retrieved 01 Apr 2010 from http://work-learning.com/effect_sizes.htm.

Additional resources may be found at:
http://www.gseis.ucla.edu/courses/ed230a2/notes/effect.html
http://web.uccs.edu/lbecker/Psy590/es.htm

Links active as of 01 Apr 2010.

Author

Matthew S. Openshaw, The University of Texas at Dallas, USA
openshaw@utdallas.edu

Please send comments, suggestions or constructive criticism to the above email address.

sizefx
v1.3
Update 01 Apr 2010