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| This program uses Cohen's d as the effect size (Dunlop, W. P., Cortina, J. M., Vaslow, J. B., & Burke, M. J. (1996). Meta-analysis of experiments with matched groups or repeated measures designs. Psychological Methods, 1, 170-177) in an equal groups paired t-test. | This program uses Cohen's d as the effect size as recommended by Dunlop, W. P., Cortina, J. M., Vaslow, J. B., & Burke, M. J. (1996) for a paired t-test. |
This program uses Cohen's d as the effect size as recommended by Dunlop, W. P., Cortina, J. M., Vaslow, J. B., & Burke, M. J. (1996) for a paired t-test.
Alpha is the (two-tailed) type I error, mdiff is the difference in group means, sd is the pooled group standard deviation with (common group)sample size inputted as n. The program then outputs the power.
Reference:
Dunlop, W. P., Cortina, J. M., Vaslow, J. B., & Burke, M. J. (1996). Meta-analysis of experiments with matched groups or repeated measures designs. Psychological Methods, 1, 170-177
[COPY AND PASTE THE SYNTAX BELOW INTO A SPSS SYNTAX WINDOW AND RUN; ADJUST DATA INPUT VALUES AS REQUIRED]
DATA LIST free /alpha mdiff sd n rho. BEGIN DATA. .05 2.0 4.0 40 0.0 .05 2.0 4.0 40 0.3 END DATA. matrix. get m /variables=alpha mdiff sd n rho /missing=omit. compute alpha=make(1,1,0). compute mdiff=make(1,1,0). compute sd=make(1,1,0). compute n=make(1,1,0). compute rho=make(1,1,0). compute alpha=m(:,1). compute mdiff=m(:,2). compute sd=m(:,3). compute n=m(:,4). compute rho=m(:,5). end matrix. COMPUTE power = 1 - NCDF.T(IDF.T(1-alpha/2,n+n-2),n+n-2,(mdiff)/SQRT((2*sd*sd/n)*(1-rho))). exe. formats n (f7.0) rho (f7.2) alpha (f5.2) mdiff (f5.2) sd (f5.2) power (f5.2). variable labels n 'Sample Size 1' /rho 'Correlation' /alpha 'Alpha' /mdiff 'Mean Difference' /sd 'SD' /power 'Power'. report format=list automatic align(center) /variables=n rho alpha mdiff sd power /title "Paired t-test power for given sample size" .