Message-ID: <1faba41f0902230905n161d05d1mb0fe2bd23f374efa@mail.gmail.com>
Date: 2009-02-23T17:05:26Z
From: choonhong ang
Subject: Insurance data in library(MASS)
I have used the insurance data from R library and I have 2 questions:
I use the following:
>library(MASS)
>data(Insurance)
> m1=glm(Claims ~ District + Group + Age + offset(log(Holders)),data =
Insurance, family = poisson)
>summary(m1)
Call:
glm(formula = Claims ~ District + Group + Age + offset(log(Holders)),
family = poisson, data = Insurance)
Deviance Residuals:
Min 1Q Median 3Q Max
-2.46558 -0.50802 -0.03198 0.55555 1.94026
Coefficients:
Estimate Std. Error z value Pr(>|z|)
(Intercept) -1.810508 0.032972 -54.910 < 2e-16 ***
District2 0.025868 0.043016 0.601 0.547597
District3 0.038524 0.050512 0.763 0.445657
District4 0.234205 0.061673 3.798 0.000146 ***
Group.L 0.429708 0.049459 8.688 < 2e-16 ***
Group.Q 0.004632 0.041988 0.110 0.912150
Group.C -0.029294 0.033069 -0.886 0.375696
Age.L -0.394432 0.049404 -7.984 1.42e-15 ***
Age.Q -0.000355 0.048918 -0.007 0.994210
Age.C -0.016737 0.048478 -0.345 0.729910
---
Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
(Dispersion parameter for poisson family taken to be 1)
Null deviance: 236.26 on 63 degrees of freedom
Residual deviance: 51.42 on 54 degrees of freedom
AIC: 388.74
(1) In the result above, what is Group.L, Group.Q, Group.C, Age.L, Age.Q,
Age.C ?
(2) When I copy the Insurance data in csv format (as shown in the
attachement) and run the same procedure the result shown is different from
above result, why ?