You are asking about support software for a book, and the book
contains the answers .... And it should be given due credit.
On Mon, 23 Feb 2009, choonhong ang wrote:
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 ?
See the book ca p.146.
(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 ?
Who knows?: you did not deign to tell us what you did with the CSV
file nor the results you got. Most likely you did not get the factor
levels and classes the same as the help file destribes. Hint: Group
and Age are ordered factors.
--
Brian D. Ripley, rip...@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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