Programming the statistical procedures from SAS

PROC MIXED heteroskedasticity univariate linear regression

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PROC MIXED heteroskedasticity univariate linear regression

I have to run a linear regression model where the residual don't have constant variance. I know there are different techniques to account for it but it is asked me to use PROC MIXED which allow non-constant variances. There are no repeated measures and my independent variable X is continuous. The code I wrote is the following:


proc mixed data=mydata;
model Y = X / solution;
repeated / group=X;

Is that right? It gives me back a warning of infinite likelihood maybe due to:

- too many variance parameters to estimates

- non variation on certain values of X

- my code is wrong


In addition, do I have do use scatterwhite degrees of freedom?

Thank you

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