I am trying to analyse some data collected from a randomised controlled trial using a mixed model. The outcome score is collected at multiple time points, however there are quite a bit of missing data so I performed a multiple imputation. I performed my mixed model and included an interaction between randomised group and time point in my model so I could obtain the mean difference between the two randomised groups at each point.
Code:
mi estimate: mixed outcome_score i.group i.time i.group##i.time c.outcome_score_baseline || ID:, covariance(unstructured)
Usually I would use a contrast statement to obtain the mean difference between the groups at each time point, however Stata will not allow a contrast statement, or event the lincom command to be run after mi estimate. and mi estimate: contrast will not work.
Code:
contrast ib2.group@i.time, effect // Group A versus Group B
I was wondering if anyone knows of a way to obtain the mean difference between the groups at each time point from a mixed model when using mi estimate. I have tried mi test but that just seems to produce P-values and not the effect.
Thanks in advance
Sam
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