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COVTEST in GLIMMIX

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Occasional Contributor
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COVTEST in GLIMMIX

Hi,

 

I ran the following program and kept getting this warning message WARNING: The initial estimates did not yield a valid objective function, and no chi2 values for the COVTEST.

 

proc glimmix method = laplace;

class mom dad;

model ontsurv (event = '1')= jsh /S dist = bin link = logit ddfm =bw;

random int/ subject = mom;

random int/ subject = dad(mom);

NLOPTIONS TECH = NRRIDG;

covtest 'var (mom)= 0'       0   .;

 

covtest 'var (dad(mom)) = 0'   . 0;

run;

 

 

 I then changed the parameter values from 0 to 0.01 and it worked – i.e.

 covtest 'var (mom)= 0'       0.0000001   .;

 

covtest 'var (dad(mom)) = 0'   . 0.0000001;

run;

 

Does anyone know why this happened, and why changing the parameter values help?

Also, I want to make sure that I understand this correctly – I am testing two random slopes (MOM and DAD) which are nested into each other, two sets of slopes?

Thanks in advance,

B

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