Hi there, I am brand new to SAS (and relatively new to statistics!) and have a question concerning how to save random slopes as variables for individual subjects in my data (n=94) using proc mixed. I have figured out how to do this for the intercepts and linear slopes but am having trouble getting estimates for the random quadratic slopes. I have done some exploration and plottings of the longitudinal data for various subgroups in my sample and know that the fixed quadratic slope for verbal IQ is negative and significant at least for the upper 20%. (VIQ accerated quickly at younger ages and then levels off during the teens). But when I run the model to get the individual estimates for the random quadratic effects, either the model does not converge or I get a message that the "Estimated G matrix is not positive definite." In the latter case, the random quadratic slopes are all predicted to be "0" (please see syntax attached). How can I get real estimates for the random quadratic slopes? I can send the actual data for the syntax file if needed. Thanks so much! Deb
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