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# Effect Size and Power? watch

1. Hiya,

Does anyone know how to calculate effect size and power from a set of results?

Thank you!
2. For effect size, it depends on which statistical test you used.

For example, for a t-test we might calculate pearson's r using the t-value:

r = sqrt(t^2/(t^2+df))

Which is as good an effect size as any ABE: (.1 small, .3 medium, .5 large).

Power is a pain in the ass to calculate, tbh. Download and use G-power (freeware) and plug in the appropriate information.
3. (Original post by Psych!)
Power is a pain in the ass to calculate, tbh. Download and use G-power (freeware) and plug in the appropriate information.
Wow, great find.
4. (Original post by Psych!)
Power is a pain in the ass to calculate, tbh. Download and use G-power (freeware) and plug in the appropriate information.
Nice one, thank you. Just wish I knew how to use it haha; no idea about this kind of stuff!
5. Well, you just need to think about what test and situation you are calculating power for.

Have you done the experiment and statistics and want an estimate of the power provided by experiment?

Or do you want a guide for how many participants would be ideal for a given degree of power that would result from a particular design, statistical test, and effect size?

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