I have done a paired t-test on a measure of self-esteem before and after a
six-week group intervention.
There is a significant difference (in the right direction!) between the
means using a paired t-test, p=.009. The effect size is .29 if I divide by
the standard deviation of the pre-test mean, and .33 if I divide by the
pooled standard deviation.
Question 1: Which is the correct standard deviation to use?
Question 2: Can an effect size of .29 (or .33) be considered clinically
significant?
Melady Preece, Ph.D.
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