R help - Nov 2004 - logistic regression and 3PL model

Hello colleagues,

 

I am a novice with R and am stuck with an analysis I am trying to conduct.
Any suggestions or feedback would be very much appreciated.

 

I am analyzing a data set of psi (ESP) ganzfeld trials.  The response
variable is binary (correct/incorrect), with a 25% base rate.  I've looked
around the documentation and other online resources and cannot find how I
can correct for that base rate when I conduct a logistic regression.  I
understand that the correction would be equivalent to the three parameter
logistic model (3PL) in IRT but am unsure how to best fit it from a logistic
regression in R.

 

Thanks much,

 

Mike Lau

 

__________________________________ 
Michael Y. Lau, M.A. 
118 Haggar Hall 
Department of Psychology 
University of Notre Dame 
Notre Dame, IN 46556 
 
  

 


	[[alternative HTML version deleted]]

The same is true in french under linux. Something changed
from 1.9.1 to 2.0.0.

First, it is necessary to have .inputrc (in $HOME) 
(or $INPUTRC defined) to enter and display 8-bits 
characters under bash and R.

#.inputrc (for readline library)
set input-meta on
set output-meta on
set convert-meta off

Then

Under R2.0.1, I have:
> ??l??ment <- "??"           # error for object name
Error: syntax error
> element <- "??"           
> element 
[1] "\351"                 # different from R1.9.1 (="??")
> Sys.setlocale('LC_ALL','fr_FR')
[1] "fr_FR"
> ??l??ment <- "??"           # OK for object name
> ??l??ment     
[1] "??"                    # OK for display

Another solution:

export LC_ALL='fr_FR'      # before loading R

and then Sys.setlocale becomes useless.

Jean Coursol

Dear Mike,

Pinheiro and Bates discuss a three-parameter logistic growth model in their
Mixed Effects Models in S and S-PLUS, but as far as I know there's no direct
way to fit the 3PL IRT model in R. It should be possible to fit such a model
using one of the general optimisers in R, such as nlm() or optimise(), and I
think that it would be a nice project to produce an IRT package for R. 

Regards,
 John

--------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario
Canada L8S 4M4
905-525-9140x23604
http://socserv.mcmaster.ca/jfox 
-------------------------------- 
> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Michael Lau
> Sent: Wednesday, November 24, 2004 10:26 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] logistic regression and 3PL model
> 
> Hello colleagues,
> 
>  
> 
> I am a novice with R and am stuck with an analysis I am 
> trying to conduct.
> Any suggestions or feedback would be very much appreciated.
> 
>  
> 
> I am analyzing a data set of psi (ESP) ganzfeld trials.  The 
> response variable is binary (correct/incorrect), with a 25% 
> base rate.  I've looked around the documentation and other 
> online resources and cannot find how I can correct for that 
> base rate when I conduct a logistic regression.  I understand 
> that the correction would be equivalent to the three 
> parameter logistic model (3PL) in IRT but am unsure how to 
> best fit it from a logistic regression in R.
> 
>  
> 
> Thanks much,
> 
>  
> 
> Mike Lau
> 
>  
> 
> __________________________________
> Michael Y. Lau, M.A. 
> 118 Haggar Hall
> Department of Psychology
> University of Notre Dame
> Notre Dame, IN 46556 
>  
>   
> 
>  
> 
> 
> 	[[alternative HTML version deleted]]
> 
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