SPSS Syntax MIXED Model

[Maguin, Eugene]

Increase the number of iterations (MXITER), maybe double the number. What happens?
I understand the message to mean that the routine failed to converge in the default number of iterations. If you read the documentation for Mixed you'll see that there are several controls for convergence.

So you get the warning message when you run this syntax (everything set at default)?

MIXED Weight WITH Time
  /FIXED = Time | SSTYPE(3)
  /METHOD = REML
  /PRINT = G SOLUTION TESTCOV
  /RANDOM = INTERCEPT Time | SUBJECT(ID) COVTYPE(UN).

What are the numbers for the random effects covariance matrix?

I'm assuming that time is days since baseline. I don't know that this would be a problem but divide the days by 10 or 20 to reduce the variance. Then run the model above.

Gene Maguin






-----Original Message-----
From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Steph Bullen
Sent: Monday, July 20, 2015 8:34 PM
To: [hidden email]
Subject: Re: SPSS Syntax MIXED Model

Hi Gene,

Thank you very much for your reply!

I have 441 calves which are allocated to two different treatments, control
(n=220) and treatment (n=221).

Calves were weighed on Day 0 (Baseline in kg) and treatment group received treatment. Calves were different ages on Day 0 and this was recorded (Age in
days)

Calves in both groups were on each farm and predominant breeds on each farm was variable but there were equal numbers of each breed (by t-test) in each group.

Calves were then weighed at approximately 6 weeks (37-50 days; depending on farm; all calves on one farm were weighed on the same day) then again at 12 weeks (80-106 days).

The error message is appearing when I run your syntax (above) with only time as the predictor. It also has an error whenever time*farm is put into the model. It is happy with all other interaction terms.

Any help/thoughts/suggestions greatly appreciated! :)

Steph






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