[R] confidence intervals on multiple comparisons

[Bert Gunter]

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of 
> Cody_Hamilton at edwards.com
> Sent: Tuesday, May 15, 2007 12:52 PM
> To: Salvatore Enrico Indiogine
> Cc: R-help at stat.math.ethz.ch; r-help-bounces at stat.math.ethz.ch
> Subject: Re: [R] confidence intervals on multiple comparisons
> 
> 
> Enrico,
> 
> prop.test is for testing proportions two at a time.  If you 
> want to test
> for differences between 4 proportions simultaneously (rather 
> than two at a
> time), try a logistic regression model (from which you can 
> get confidence
> intervals for each of your groups).
> 
> Cody Hamilton, PhD
> Staff Biostatistician
> Edwards Lifesciences
> 

Yes, but beware: in the default contr.treatment coding for contrasts, you
get estimates and confidence intervals for the first group and for the
**differences** between the first group and the others. As you said, it's
easy to get what you want from this, but you must pay attention to the
details here. 

Bert Gunter
Genentech Nonclinical statistics


>                                                               
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>              "Salvatore Enrico                                
>              
>              Indiogine"                                       
>              
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>      Subject 
>                                        [R] confidence 
> intervals on         
>                                        multiple comparisons   
>              
>              05/13/2007 10:51                                 
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> 
> 
> Greetings!
> 
> I am using prop.test to compare 4 proportions to find out whether they
> are equal.  According to the help function you can not have confidence
> intervals if you compare more than 2 proportions.
> 
> I need to find an effect size or confidence interval for 
> these proportions.
> 
> Any suggestions?
> 
> Enrico
> 
> --
> Enrico Indiogine
> 
> Mathematics Education
> Texas A&M University
> hindiogine at gmail.com
> 
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> PLEASE do read the posting guide 
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> and provide commented, minimal, self-contained, reproducible code.
>