Model with categorical * continuous variable interactions in JASP
Hi JASP team,
I have run a frequentist moderated regression with two binary categorical predictors (group, sex), four continuous predictors (e.g., IQ), and interactions between the group categorical variable and each of the other predictors (i.e., group*sex, group*IQ etc). All variables mean centred / effect coded.
I’m now looking to run a Bayesian equivalent analysis in JASP, to obtain inclusion Bayes factors for each of the predictors and interaction terms.
I was intending to use Bayesian ANCOVA for appropriate uninformative priors, categorical variables as fixed factors, continuous as covariates, and manually entering the interaction terms in the model options. I would report the BFincl across matched models. Is this the best approach? I’m unsure of the appropriateness of including interactions between factors and covariates in ANCOVA, particularly following assumptions of homogeneity of regression slopes. I noticed while the effects table computes, I have received errors in the estimates table for the interaction terms (NaN for Mean and SD; 0 for credible intervals). I wasn’t intending on reporting the estimates table so this is not a problem, but are the results from the rest of the analysis valid? Is there an alternative method I should use?
Many thanks for your help.