Posted by
Hector Maletta on
Aug 23, 2006; 3:32pm
URL: http://spssx-discussion.165.s1.nabble.com/Re-interpretation-of-the-warning-message-tp1070503p1070507.html
You probably were doing it stepwise, and the procedure failed to converge at
some step, so it judged it wise to stop at that step and not trying to
introduce further variables. Or perhaps you were doing it in a single step,
and the model simply did not converge. It just happens sometimes, when the
data fail to fit the model.
The reasons may vary. Increasing the number of iterations seldom helps.
Relaxing the convergence criterion is close to cheating and seldom
advisable. Also, it seldom works either (the failure to converge is often by
a much wider margin than any reasonable relaxation you may introduce in the
convergence criterion). Perhaps you have too few cases to arrive at a
significant solution, or perhaps the model is poorly specified. Perhaps the
hazards are not proportional, so Cox does not apply unless some time-related
covariates are introduced. Try to modify the model, e.g. introducing
time-varying covariates, or changing the list of covariates by withdrawing
some of them that seem to have less strong relationship with the event of
interest. Perhaps you may try some simpler models first, to see whether the
covariates fit the data (predict survival) one by one, or in pairs, before
running a more complicated model. Sorry to say I do not have a magic bullet,
but this, as poetry, is more perspiration than inspiration.
Hector
-----Mensaje original-----
De: SPSSX(r) Discussion [mailto:
[hidden email]] En nombre de
Yampolskaya, Svetlana
Enviado el: Wednesday, August 23, 2006 11:20 AM
Para:
[hidden email]
Asunto: Re: interpretation of the warning message
Dear List,
I am trying to do Cox regression (bivariate analysis) and I have this
message that I cannot interpret.
Can you please help and tell me what was wrong?
Warnings
Since coefficients did not converge, no further models will be fitted.
Thank you,
Lana