Ibrahim H Acar

2 Questions 7 Answers 0 Followers

Questions related from Ibrahim H Acar

What does "Estimated G matrix is not positive definite" mean?

I've run a random intercept only model SAS PROC MIXED and it gives me a notice on log window saying "Estimated G matrix is not positive definite". Do you think I should concern about it? Or keep...

01 January 2016 6,700 6 View

Why does sign change in interaction term after adding control variables?

When I added some control variables at Level 1 in a Multilevel Model, my interaction term changes its sign from positive to negative as well my main effect of one variable. Why is that happening?...

12 December 2015 4,038 6 View