You don't.
And even if you do get someone to tell you how, you may still not
legitimately lower your degrees of freedom. Friends don't let friends
use stepwise approaches to regression analysis.
--
David Winsemius
On Feb 25, 2009, at 10:33 PM, choonhong ang wrote:
The district a is the baseline and we observe the difference between
District a & b is not significant, we can choose to combine these 2
values.
How to write code to combine these 2 value ?
m1=glm(Claims~District+Group+Age+log(Holders),fami
ly=poisson,data=mydata)
summary(m1)
Call:
glm(formula = Claims ~ District + Group + Age + log(Holders),
family = poisson, data = mydata)
Deviance Residuals:
Min 1Q Median 3Q Max
-2.553115 -0.471819 0.002411 0.455274 1.800739
Coefficients:
Estimate Std. Error z value Pr(>|z|)
(Intercept) -2.777752 0.689162 -4.031 5.56e-05 ***
Districtb 0.119942 0.079861 1.502 0.133125
Districtc 0.228371 0.144503 1.580 0.114019
Districtd 0.571661 0.248792 2.298 0.021576 *
Group>2l 0.794721 0.180354 4.406 1.05e-05 ***
Group1-1.5l -0.003496 0.127947 -0.027 0.978202
Group1.5-2l 0.379190 0.055856 6.789 1.13e-11 ***
Age>35 -1.074971 0.389480 -2.760 0.005780 **
Age25-29 -0.332131 0.129512 -2.564 0.010333 *
Age30-35 -0.539815 0.160138 -3.371 0.000749 ***
log(Holders) 1.201696 0.144135 8.337 < 2e-16 ***
---
Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
(Dispersion parameter for poisson family taken to be 1)
Null deviance: 4236.68 on 63 degrees of freedom
Residual deviance: 49.45 on 53 degrees of freedom
AIC: 388.77
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______________________________________________
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and provide commented, minimal, self-contained, reproducible code.
