[R] Probit Analysis

[Ngayee J Law]

Hi Andy,

Thanks! glm and dose.p can do exaclty what I want to do. Just a quick
question,
how can I extract the numbers in the glm.dose object created by the dose.p?
My
goal is to calculate a 95% CI for the 'LD50'.

- Jacqueline




                                                                                                                
                    apjaworski at mm                                                                               
                    m.com                To:     "Ngayee J Law" <Ngayee.Law at celeradiagnostics.com>              
                                         cc:     r-help at stat.math.ethz.ch                                       
                    12/31/2002           Subject:     Re: [R] Probit Analysis                                   
                    02:47 PM                                                                                    
                                                                                                                
                                                                                                                





Jacqueline,

This should be a simple application of GLM.  Check the help pages for glm,
family and dose.p in library MASS.  Look at the example at the bottom of
the dose.p help page - it does almost exactly what you need.

Hope this helps,

Andy

__________________________________
Andy Jaworski
Engineering Systems Technology Center
3M Center, 518-1-01
St. Paul, MN 55144-1000
-----
E-mail: apjaworski at mmm.com
Tel:  (651) 733-6092
Fax:  (651) 736-3122


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Hello all,

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

X    Event          Trial
100  8         8
75   8         8
50   6         8
25   4         8
10   2         8
0    0         8

I want to estimate the value of X that will give a 95% hit rate
(Event/Trial) and the corresponding
95% CI. Anyone can offer some help? Thanks!!

- Jacqueline

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