Bayesian Paired Samples t test effect size

jweir48

How is the effect size in the Bayesian paired sample t test calculated? The "median" effect size in the Bayesian inferential plot is not the same as the Cohen's d (which here is the mean diff/SD of the difference scores, ie the dz) calculated from the frequentist paired samples t test in JASP.

Thanks in advance.

Joe

EJ

Hi Joe,

population effect size delta = population mu / population sd.

So it's the population equivalent of Cohen's d (which is a summary based on the sample, not an inference)

Cheers,

E.J.

jweir48

Thanks EJ. Much appreciated. Is there a reference you can point me to that would help me wrap my head around it better?

Joe

EJ

There's a 2009 paper in Psychonomic Bulletin & Review by Rouder & Morey:

@ARTICLE{RouderEtAl2009Ttest,

 AUTHOR =    {Rouder, J. N. and Speckman, P. L. and Sun, D. and Morey, R. D. and Iverson, G.},

 TITLE =    {{B}ayesian $t$ Tests for Accepting and Rejecting the Null Hypothesis},

 JOURNAL =   {Psychonomic Bulletin \& Review},

 YEAR =     {2009},

 volume =    {16},

 pages =    {225--237},

}

jweir48

Awesome. Thanks! Very helpful. I owe you a beer.

Joe