Each center have 200 (different) patients, which makes patient nested within center for sure. But i am not sure that applies here, since nested logit works in case of decision trees with choices for the second level are nested within the levels of the first level, e.g choosing center and within center there would be different choices (treatment A and B in center 1, treatment C and D in center 2, etc.) Center*choice worked for sure, it gives you an estimate for the choice per center. However, i want to estimate the center effect itself, in addition to the interaction effect. In other procedures (in a hypothetical situation), e.g. GENMOD , this is done by: model choice_patient=center choice center*choice. This approach, however, does not seem to work with MDC. Any suggestions Steve? Thanks in advance.
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