R scale fixed effects and r scale random effects in Bayesian ANOVA.

IngevanderBorg

Hello,

For my Bachelor thesis I've done a Bayesian ANOVA in JASP for which i used the default prior settings. Can somebody please explain to me what the 'r scale fixed effects' and 'r scale random effects' mean? to optimize my prior settings. Thank you very much in advance!!

Kind regards,

Inge van der Borg

EJ

Hi Inge,
The ANOVA model is not so simple. I advice you to start with http://www.ejwagenmakers.com/inpress/RouderEtAlinpressANOVAPM.pdf
We are working on a JASP Manual that will explain these in a language that is perhaps easier to understand, but that's work in progress.
Cheers,
E.J.

IngevanderBorg

Dear Dr. Wagenmakers,

I've read your paper with great interest. Thank you very much. I do have one question. Is it true that 'h' as mentioned in this paper is represented by the r scale fixed effects prior in JASP?

Kind regards,

Inge van der Borg

EJ

Hi Inge,

From memory, yes. But if you want to know for sure you should drop Richard Morey an Email. Another way to check is to consult the BayesFactor documentation, or run the same analysis in JASP and BayesFactor. It is always best to check for yourself than to take anybody's word.

Cheers,
E.J.

dontchaknowjo

Hi EJ,

That link no longer works. Do you have an updated version?

EJ

Sorry about that. Here it is:
http://www.ejwagenmakers.com/2017/RouderEtAl2017ANOVAPM.pdf

Cheers,
E.J.

marmite

Hi EJ,

Thanks for providing some insight on this.. doesn't seem to be discussed anywhere!

I'm still confused as how to choose an 'h' value. I have some pilot data where I did a paired t-test between two groups and so I have a difference in means and the effect size in Cohen's d units.

I am now looking to run an ANOVA which includes one more group than the pilot. How do I use these data to inform my h prior?

Cheers