Re: [R] logistic regression or not?

2010-12-21 Thread array chip
Ben, thanks again. John From: Ben Bolker Cc: r-h...@stat.math.ethz.ch; S Ellison ; peter dalgaard Sent: Tue, December 21, 2010 9:26:29 AM Subject: Re: [R] logistic regression or not? On 10-12-21 12:20 PM, array chip wrote: > Thank you Ben, Steve and Pe

Re: [R] logistic regression or not?

2010-12-21 Thread Ben Bolker
package) is another way of handling analysis of proportions. > > > *From:* Ben Bolker > *To:* r-h...@stat.math.ethz.ch > *Sent:* Tue, December 21, 2010 5:08:34 AM > *Subject:* Re: [R] logistic regression or not? > > array chip ya

Re: [R] logistic regression or not?

2010-12-21 Thread array chip
: glm(log(percentage/(1-percentage))~treatment,data=test) Thanks John   From: Ben Bolker To: r-h...@stat.math.ethz.ch Sent: Tue, December 21, 2010 5:08:34 AM Subject: Re: [R] logistic regression or not? array chip yahoo.com> writes: [snip] > I can th

Re: [R] logistic regression or not?

2010-12-21 Thread S Ellison
>...and before you believe in overdispersion, make sure you have a credible explanation for it. All too often, what you really have >is a model that doesn't fit your data properly. Well put. A possible fortune? S Ellison *** Th

Re: [R] logistic regression or not?

2010-12-21 Thread peter dalgaard
On Dec 21, 2010, at 14:22 , S Ellison wrote: > A possible caveat here. > > Traditionally, logistic regression was performed on the > logit-transformed proportions, with the standard errors based on the > residuals for the resulting linear fit. This accommodates overdispersion > naturally, but wi

Re: [R] logistic regression or not?

2010-12-21 Thread S Ellison
A possible caveat here. Traditionally, logistic regression was performed on the logit-transformed proportions, with the standard errors based on the residuals for the resulting linear fit. This accommodates overdispersion naturally, but without telling you that you have any. glm with a binomial f

Re: [R] logistic regression or not?

2010-12-21 Thread Ben Bolker
array chip yahoo.com> writes: [snip] > I can think of analyzing this data using glm() with the attached dataset: > > test<-read.table('test.txt',sep='\t') > fit<-glm(cbind(positive,total-positive)~treatment,test,family=binomial) > summary(fit) > anova(fit, test='Chisq') > First, is this still

[R] logistic regression or not?

2010-12-20 Thread array chip
Hi, I have a dataset where the response for each person on one of the 2 treatments was a proportion (percentage of certain number of markers being positive), I also have the number of positive & negative markers available for each person. what is the best way to analyze this kind of data? I can