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st: Convergence not achieved in negative binomial regression modeling
From
Vineet Saini <[email protected]>
To
"[email protected]" <[email protected]>
Subject
st: Convergence not achieved in negative binomial regression modeling
Date
Sat, 09 Jul 2011 06:30:07 -0600
Dear Statalist users,
I am running stepwise nbreg to model antimicrobial resistance in bacteria
and I get the message that "convergence not achieved" as following:
. stepwise, pr (0.95) pe(0.90) :nbreg penr_tot pnbdctuse cs1dctuse lnlctuse
cs3lctuse pnclctuse pnsysuse cs3sysuse tmpsysuse tetsysuse phnsysuse
herddurd_cn zone barntype [pw=weight], exp(farmcowday_tot) irr
convergence not achieved
convergence not achieved
r(430);
Later, I inserted -iterate (500) in the command, and then got the following
output:
. stepwise, pr (0.95) pe(0.90) :nbreg penr_tot pnbdctuse cs1dctuse lnlctuse
cs3lctuse pnclctuse pnsysuse cs3sysuse tmpsysuse tetsysuse phnsysuse
herddurd_cn zone barntype [pw=weight], exp(farmcowday_tot) iterate(50) irr
begin with full model
p < 0.9500 for all terms in model
Negative binomial regression Number of obs =
79
Dispersion = mean Wald chi2(13) =
226.58
Log pseudolikelihood = -50010.674 Prob > chi2 =
0.0000
----------------------------------------------------------------------------
--
| Robust
penr_tot | IRR Std. Err. z P>|z| [95% Conf.
Interval]
-------------+--------------------------------------------------------------
--
pnbdctuse | 1.652111 .4883559 1.70 0.089 .9256107
2.948833
cs1dctuse | .2436561 .1924028 -1.79 0.074 .0518354
1.145322
lnlctuse | 1.088507 .1223067 0.75 0.450 .8733506
1.356669
cs3lctuse | 18.87842 11.36569 4.88 0.000 5.800991
61.43685
pnclctuse | .7654628 .0987489 -2.07 0.038 .5944488
.985675
pnsysuse | .5867255 .1123691 -2.78 0.005 .4031008
.8539967
cs3sysuse | .8746823 .0965915 -1.21 0.225 .7044527
1.086047
tmpsysuse | 1.464673 .27624 2.02 0.043 1.012052
2.119722
tetsysuse | 1.657977 .2532772 3.31 0.001 1.228985
2.236714
phnsysuse | 14.31775 5.312295 7.17 0.000 6.919181
29.62749
herddurd_cn | .0261432 .0185816 -5.13 0.000 .0064917
.1052835
zone | 1.986719 .3173496 4.30 0.000 1.452678
2.717087
barntype | .1920082 .1312393 -2.41 0.016 .050294
.7330328
farmcowday_tot| (exposure)
-------------+--------------------------------------------------------------
--
/lnalpha | -17.92744 . .
.
-------------+--------------------------------------------------------------
--
alpha | 1.64e-08 . .
.
1. Has the model converged and how do I know that?
2. What does the blanks (dots) for robust SE and 95% CI for /lnalpha and
alpha indicate? That the model has still not converged??
Thanks a lot,
Vineet
--
Vineet Saini
PhD Candidate
Faculty of Veterinary Medicine
The University of Calgary
HS 3330, Hospital Drive, NW
Calgary, AB, Canada T2N 4N1
Email: [email protected]
Tel: 403.975.7919 (cell)
403.210.6813 (work)
"Until we see what we are, we cannot take steps to become what we should be"
~ Charlotte P. Gilman ~
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