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# Comparing models following Bayesian ANOVA

Hello! Hope someone can point me in the right direction. I know the concept but unsure how to process it via JASP.

I have 2 independent variables, A and B. I have done a Bayesian ANOVA to compare the following model:

1. A vs Null
2. B vs Null
3. A + B vs Null
4. A + B + A*B vs Null

So far so good! But I also need to compare the following:

1. A + B + A*B vs A + B
2. A + B vs B
3. A + B vs A

I am assured this is easily achievable in JASP! I tried to add variables to null hypothesis under the 'model' tab, but I'm unsure this is the correct way. I can obtain Bayes Factors using this method for 6 and 7, but adding A, B, and A*B to null model for 5 produces an error under nuisance variables.

Any pointers greatly appreciated!

H.

• Dear H.,

Yes, this is easily achievable, in two ways. For concreteness, suppose you want A+B+AB vs A+B.
Method 1. Add "A" and "B" to the null model (under the "model" tab).
Method 2. Use transitivity: if you already have BFfull = A + B + A
B vs Null and BFmain = A + B vs Null, then the BF in favor of the full model over the two main effects model is BFfull / BFmain.
Both methods ought to give the same results. The other comparisons you are interested in can be obtained similarly.

Cheers,
E.J.

• Thank you, EJ.

I've since learned how to do these multiple model comparisons in a table by hand to obtain the ratios (as you say, full/main) but great to learn how to do this in JASP too. This is our first time using it.

Cheers!
H.