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I am working on a power analysis project- we are reviewing old journal
articles to calculate observed effect sizes and power. Some of these
articles, for example reporting t-test results, only give means and
t-test, no standard deviation. thus, no effect size calculation is
possible. I was hoping to estimate an effect size by converting a t to
an r. I seem to remember a formula that relates the two, but am having
a dickens of a time tracking one down. The one I did track down, for
calculating t from r, is not that helpful:
t= r * sqrt(n-2)
-------------
sqrt(1-r^2)
I want to be able to calculate r from t. I tried algebraically
manipulating the formula, but never quite got it to where I could do
this. Any advice?
Alternatively, a formula for converting t or F to eta-squared, which is
roughly analogous to r-squared, would also be helpful (I know they are
not exactly analogous).
Thanks in advance,
Jason
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