PSPP for Beginners: Cohen's d for independent-samples t-tests

How to calculate Cohen's d for independent-samples t-tests

The strategy is to use the descriptive statistics from an independent-samples t-test output. Enter the appropriate values into the fields below. See the one-sample t-test page for a similar example.

This screenshot is an example from the independent-samples t-test output. The default calculator means have already been entered as default values in the data fields. Click on the button to get the Cohen's d value.

This screenshot from an independent-samples t-test output has descriptive statistics (means and standard deviations) needed for the Cohen's d calculation.













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Notes

This version of Cohen's d is for independent-samples t tests. It uses pooled standard deviations.

Suggested effect size interpretation (Sawilowsky, 2009):

These value labels are not meant to be absolute standards. The interpretation depends upon the research context.

References

Datanovia.com T-test Effect Size using Cohen's d Measure

Sawilowsky, S.S. (2009). New effect size rules of thumb. Journal of Modern Applied Statistical Methods. 8(2), 597-599. https://doi.org/10.22237/jmasm/1257035100

Wikipedia: Effect size


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