[R] probit analysis

From: Jinsong Zhao <jszhao_at_mail.hzau.edu.cn>
Date: Sat 06 May 2006 - 17:08:33 EST


Dear all,

I have a very simple set of data and I would like to analyze them with probit analysis.

dose event trial

0.0 3  15
1.1 4  15
1.3 4  15
2.0 3  15
2.2 5  15
2.8 4  15
3.7 5  15
3.9 9  15
4.4 8  15
4.8 11 15
5.9 12 15
6.8 13 15

The dose should be transformed with log10().

I use glm(y ~ log10(dose), family=binomial(link=probit)) to do probit analysis, however, I have to exclude the first observation. In an experimental design, the first observation may be as a control group. I think it should not be simple excluded from the datasets when constructing a model.

I refered to SAS online doc for probit procedure, it use the first observation to estimate the natural (threshold) response rate (C). And the final model will be:

p = Pr(Y = 0) = C + (1 - C)F(x'\beta)

However, I don't know how to considered the control effect when using glm().

Any suggestions will be really appreciated.

Best Regards,

Jinsong Zhao



R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sat May 06 17:13:35 2006

Archive maintained by Robert King, hosted by the discipline of statistics at the University of Newcastle, Australia.
Archive generated by hypermail 2.1.8, at Sat 06 May 2006 - 18:10:03 EST.

Mailing list information is available at https://stat.ethz.ch/mailman/listinfo/r-help. Please read the posting guide before posting to the list.