Hello everyone,
I am testing for statistical interaction between two variables in a logistic regression model and I am finding that from a biologically plausible level the interaction changes. However, I want to back up this finding statistically so I have an additional argument for stratification. Therefore I added a three way interaction as continuous1*continuous2*cut-off continuous2, with p=0.01, so fitting with my observation.
Can anybody tell me whether this is valid and perhaps provide me with some evidence (I am so far unable to find any papers)?