logistic regression and 3PL model
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]] ______________________________________________ R-help at 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