@AW92 wrote:
Hi Paige,
Thanks again.
From your answer, specifically the use of "id" as a covariate, am I correct in concluding that the use of fixed-effects regression is inappropriate for situations where you require future predictions for subjects whose "id" does not exist in the training data?
Yes, but so is using the ABSORB statement.
There's no logical way around this, if the data does not contain "id" values of future observations, the model can't predict when you get one of the future "id" values. This has nothing to do with SAS, it is a logical impossibility. What most people would do in this case is when the future "id" values arrives, they perform some statistical testing to estimate the mean value of the response variable for this future "id" value.
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