Hi all,
I am trying to use a mixed effects model with a random intercept for a project, but I am not sure my output is correct. My code is as follows:
proc mixed data=pf;
class timepoint(ref="0") tx_arm(ref="Tx");
model TOTAL_SCORE=timepoint tx_arm timepoint*tx_arm/ solution;
repeated timepoint/ sub=username(tx_arm) type=un r rcorr;
run;
I keep getting an error message in the output as follows:
Convergence criteria met but final hessian is not positive definite.
Can someone tell me where I am going wrong? Thank you.
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