The following formula is involved in the calculation of Cohen's d effect size values for t-tests:
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Cohen's d effect size for a t-test:
where x1 and x2 are the means of group 1 and group 2, and σ12 and σ22 are the variances of group 1 and group 2.
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The following references can be used to cite this effect size (cohen's d) calculator for a student t-test:
| Soper, D.S. (2013). Effect Size (Cohen's d) Calculator for a Student t-Test [Software]. Available from http://www.danielsoper.com/statcalc |
| Cohen, J. (1988). Statistical Power Analysis for the Behavioral Sciences (2nd Edition). Hillsdale, NJ: Lawrence Earlbaum Associates. |