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Author Topic: Effect Size for Paired T-test  (Read 21406 times)
august_leo
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« on: April 19, 2010, 10:24:12 am »

How do you calculate effect sizes for paired t-tests?

I usually use Cohen's d for my effect sizes, which I calculate manually in excel for one-sample t-tests against chance. I sometimes use this calculator to do them quickly for conference submissions, etc. I don't have a routine for paired t-tests.

I found one calculator for this online, but the values seem too low....
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resis
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« Reply #1 on: April 19, 2010, 3:53:32 pm »

r = square root of (t-squared / [t-squared + degrees of freedom])

or if you prefer the coefficient of determination,

r-squared = t-squared / (t-squared + degrees of freedom)

Source:

p. 19 of Rosenthal, Robert (1991) Meta-analytic procedures for social research (revised). Newbury Park, CA: Sage.

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drspouse
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« Reply #2 on: April 23, 2010, 12:13:05 pm »

Hi august_leo

I use a variety of online calculators including:

http://www.cognitiveflexibility.org/effectsize/

http://www.stat.uiowa.edu/~rlenth/Power/index.html

You can usually find what you need here

http://statpages.org/
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august_leo
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« Reply #3 on: April 23, 2010, 6:18:24 pm »

Thanks, resis and Dr Spouse!

(my internet hasn't been working at home, so it took a while to get back to the fora.)
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