sdm-help-list > Can SDM effect sizes be used in an a priori power analysis
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Oct 31, 2022  03:10 PM | scchester
Can SDM effect sizes be used in an a priori power analysis
Dear all, 

I am preparing an analysis plan for a mega-analysis (meta-analysis with de-identified individual participant data). I have been advised to include an a priori power analysis to calculate the required sample size per group to achieve 80% power using the G*Power power analysis tool.

My question is - can I use SDM estimates, reported in a previous meta-analysis, as inputs in this power analysis tool? Can they be used in place of the usual Cohen's d? Are SDM estimates equivalent to a Cohen'd effect size (i.e. small (d = 0.2), medium (d = 0.5), and large (d = 0.8)?


Many thanks for your help with this matter!

Kind regards,
Sally
Nov 1, 2022  10:11 AM | Lydia Fortea - Instituto de Investigaciones Biom├ędicas August Pi i Sunyer (IDIBAPS)
RE: Can SDM effect sizes be used in an a priori power analysis
Dear Sally, 

You can use the output Hedges'g from the SDM, which are corrected Cohen's d; and in this case, they are equivalent to the effect size

Kind regards, 
Lydia
Nov 1, 2022  04:11 PM | scchester
RE: Can SDM effect sizes be used in an a priori power analysis
Dear Lydia, 

Thank you very much for your swift response!!

Are you able to tell me where in the SDM outputs the Hedges g can be found?

Kind regards,
Sally
Nov 1, 2022  05:11 PM | Lydia Fortea - Instituto de Investigaciones Biom├ędicas August Pi i Sunyer (IDIBAPS)
RE: Can SDM effect sizes be used in an a priori power analysis
Dear Sally, 

In the SDM window, once you have performed the meta-analyisis, you click in the "Extract" buttom, and select one desirable peak (you should do this for every significant peak). This will create a report with the Hedges'g 

Kind regards, 
Lydia