"wide" scale has different meaning for anovaBF and ttestBF (BayesFactor in R)?
reading the docs for the BayesFactor package, it states for the anovaBF argument rscaleFixed: "medium","wide","ultrawide", corresponding to r scale values of 1/2, √2/2, and 1, respectively.
For the ttestBF, the scale argument states: "medium", "wide", and "ultrawide". These correspond to r scale values of √2/2, 1, and √2 respectively.
So a Cauchy prior with scale of √2/2 would be "wide" in the anovaBF and "medium" in the ttestBF, correct?
If so, is there a reason for this?
Thanks for the clarification!
Comments
This has to do with the parametrization of the models. I believe the that in the t-test the prior is on the difference between the two means, whereas in the ANOVA it is on the difference to the grand mean. You can confirm by conducting both a t-test and an ANOVA on the same data (i.e., a comparison of two conditions).
Cheers,
E.J.