I've recently started analysing the data for a project using linear mixed models but am not sure how to deal with a predictor that depends on another.
In my study, each participant reported two events (Event: A & B) and whether they discussed each event with someone else (Status: shared or not shared). In other words, besides event which was a within subjects predictor, I also have two responses from each participant regarding status for each event. A participant can have discussed Event A but not Event B (or the vice versa), both events, or neither of the events. The dependent variable is perceived emotional change.
I initially structured the model in this way:
mod = smf.mixedlm("emotion_change ~ Event * Status", data, groups=data["participant"]).fit()
However, I realised that the model should probably be hierarchical because each Status response was specifically for one of the events, so I created two variables instead: Status_PE and Status_NS, and the new model looked like this:
mod = smf.mixedlm("emotion_change ~ Event * Status_PE * Status_NS", data, groups=data["participant"]).fit()
Then, I realised putting all these three predictors together may not be a good idea because Status_PE interacting with Status_NS doesn't make sense, so I adjusted it this way:
mod = smf.mixedlm("emotion_change ~ Event + Status + Event : Status_PE + Event : Status_NS", data, groups=data["participant"]).fit()
But the problem now is, I’m looking at the effects of each event on emotional change based on whether the event was discussed, but what I also want to test is whether there’s any difference in the outcome variable between different combinations of event and status. For example, let’s say I know that discussing an event makes people experience greater emotional change than not discussing an event, but this observation may only applies to one of the events.
So, my question is how I should deal with the IVs that are not independent of each other and how I should structure the model to test what I want to test?
Thank you for reading my question!
source https://stackoverflow.com/questions/72062776/linear-mixed-models-with-one-predictor-depending-on-another-in-python
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