Perhaps a better question would be: Is it necessary for the subject and withinsubject variables to identify a unique observation. In the previous example, if I let the policyholder be the subject, and the year the claim was made be the withinsubject identifier, there would be cases with more than one observation having the same values for the subject and withinsubject variables. For example there would be two observations with policy id A and 2009 as the year in which the claim was paid. Is that ok?
Never mind, I just realized the withinsubject variable must have as many levels as there are observations for the subject.
Message was edited by: HMedina
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