[R] probit analysis
arun
smartpink111 at yahoo.com
Tue Jun 5 06:13:05 CEST 2012
Hi Trinh,
Please check ?dose.p() from library MASS.
Since you wanted the rate, the code was a bit modified from the example.
> datPr
X Event Trial
1 1210.0 8 8
2 121.0 6 8
3 60.5 6 8
fm<-glm(Event/Trial~X,data=datPr,family=quasibinomial(link=probit))
XD50<-dose.p(fm,cf=1:2,p=0.5)
Dose SE
p = 0.5: -203.7126 105.3647
XD50_CI<-XD50+c(1,-1.96,1.96)*attr(XD50,"SE")
names(XD50_CI)<-c("XD50","lower","upper")
XD50_CI
XD50 lower upper
-98.347938 -410.227309 2.802128
I am not very confident about the results though.
A.K.
From: phale_chuong gionho <phale_chuonggionho at yahoo.com>
To: "r-help at r-project.org" <r-help at r-project.org>
Cc:
Sent: Monday, June 4, 2012 10:52 AM
Subject: [R] probit analysis
Hello!
> I have a very simple set of data and I would like to analyze
> them with probit analysis.
> The data are: X Event Trial
> 1210 8 8
> 121 6 8
> 60.5 6 8
> I want to estimate the value of X that will give a 95% hit
> rate (Event/Trial) and the corresponding 95% CI.
> you can help me? Thanks!!
> Trinh
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