Hello, everyone!
I have a model that incorporates race as (Whites vs other) and ethnicity as (Hispanic vs not). The PI wants to look at non-Hispanic Whites vs all others as a contrast. This is easily enough done by including the interaction in the model and writing:
lSMestimate race2*hispanic2 'All Others vs. Non-Hispanic White' 1 -3
1 1 / divisor = 3;
It turns out that this interaction is very not significant (Type 3 p = 0.70). I realize that the interaction staying in the model while not significant is not likely to affect my results much. But if I did want to remove the interaction from the model and rerun, could I still do the same comparison: non-Hispanic Whites vs all others? I've written this code, and it's estimable, but my hunch is that theoretically, the model can no longer say anything about a combination of the two groups, even though I technically can form the estimates and compare their difference.
*estimate 'Hispanic Non-White' intercept 1 race2 0 1 hispanic2 1 0;
*estimate 'Non-Hispanic Non-White' intercept 1 race2 0 1 hispanic2 0 1;
*estimate 'Hispanic White' intercept 1 race2 1 0 hispanic2 1 0;
estimate 'Avg. of All Others' intercept 3 race2 1 2 hispanic2 2 1 (divisor = 3),
'Non-Hispanic White' intercept 1 race2 1 0 hispanic2 0 1,
'Avg. of All Others vs. Non-Hispanic White' race2 -2 2 hispanic2 2 -2 (divisor = 3);
This does give an answer in the same ballpark as the model with the interaction, which might be expected since the interaction was not significant.
My reason for asking is because my real model has 8 racial groups and 3 ethnicity groups, and running the model with an interaction is not possible (quasi-complete separation in logistic). I dichotomized race and ethnicity to get an answer to the study question, but I am just curious if I could have kept the full responses, omitted the interaction, and still answer the question. The answer I get when I do that is very different from either of the dichotomized answers above. I want to understand if that difference is likely because what I did is invalid or if keeping all the detail about the other racial and ethnic categories might really have changed the result a lot.
Warm regards,
Michael
Thank you! And duh! I don't know why I just didn't make a combined variable. It's so obvious now, haha.
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