I did an experiment and there are 3 treatments. My hypothesis is that treatment A & C will lead to response 1 and treatment B will lead to response 0. I'm not trying to get a comparison result like "compared with B, A is more likely to cause 1". So I don't want a reference category.
My initial fomula: logit(y) = b0 + b1 * treatment + b2 * quantitative_predictor_1 + ...
This seems not working as I wish in SPSS or R.
I searched and read the question here (Can multiple logistic regression be performed without a reference/baseline?) but I'm not sure if OP was asking the same question as mine. I read the no constant/intercept approach but I don't know if it fits my situation.
Besides that, I don't know how to do this outside Stata like the answer suggested, and I'm not sure how to apply this in multilevel analysis (my subjects were measured several times within a period of time, I've tried lme4).
Please help, share your statistical expertise and experience with statistics software/package. Thank you!
I realized that what I need to test the hypothesis is a null model like 'A, B, C, cause outcome 1 or 0 randomly (odds-ratio=1)'. This is the reference group I need, not A, B, or C. If I only have the variable treatment (A, B, C) and the outcome (1, 0), a Chisq-test or Fisher-test can show there are group differences (and I guess the reference is '3 groups have similar percentages of 0s and 1s'). With all the other variables, I want to push for logistic regression, although my thinking might be wrong.