Hello, I am trying to run a repeated measures analysis in proc mixed and am not sure how to handle a repeated aspect of the experiment that generated this data. The experiment investigated the effects of weather on rodent foraging in foraging patches (the response is the amount of grain left after a night a foraging). We measured this in 12 different sites for 19 different sessions. Within each session, we measured grain for 3 nights. Here is an example of the data: site session night grain_left 1 1 1 1.66 1 1 2 1.50 1 1 3 1.57 1 2 1 1.52 1 2 2 1.48 1 2 3 1.41 2 1 1 1.10 2 1 2 0.98 2 1 3 0.83 2 2 1 0.66 2 2 2 0.59 2 2 3 0.55 I expect the results for each site to be closely correlated for the 3 nights within each session but also expect some (lesser) correlation from session to session. I have found examples of how to handle data with nesting (e.g., providers nested in hospitals) but I have not seen examples of how to handle nesting of time within time (nesting night within session). Based on what I have read, I think this may be an appropriate way to code this: proc mixed data=grain_left method=REML; class site night session; model grain_left = weather_variables /solution residual ddfm=satterthwaite; repeated night(session) /subject=site type=ar(1); run; This code runs, but I am not certain this is the best way to code this. Could anyone share any thoughts on whether this is appropriate, and if not, a better way to handle this? Or recommend resources that discuss this kind of experimental design? Thanks very much!
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