I'm not sure if this has been posted before but I noticed that getting the effect size for pairwise comparisons in ANOVA directly through the jamovi program yields different results from running the exact same analysis through R.

For instance, one of the pairwise comparisons has VAR1 (n = 75) with M ± SD = 6.8 ± 3.5 and VAR2 (n = 74) with M ± SD = 4.5 ± 3.0, which comes out to be approximately a cohen's d of ~0.7. This seems to be calculated correctly in the jamovi application but when I run the same analysis through R, the cohen's d comes out to be around around d = 0.25. All other metrics (e.g., p-value, test statistic, etc.) are the same, however.

From doing a bit of calculation, it looks like the ANOVA cohen's d calculation when done through R is dividing the Cohen's d calculation by a constant of 2.81898 (I have a 2x2 factorial two-way ANOVA). Is this the program in R erroneously applying a Bonferroni-style adjustment to the Cohen's d?

*I'm using jamovi v.1.8.1.0 and I've updated the jmv/jmvcore packages on R but am still getting the same issue. I ran the same analysis through the jamovi program's R editor module and it's coming out correctly, so it seems isolated to just R.