Hello -- I am curious if lmer can be used to fit a multilevel factor model such as a two-parameter item response model. The one parameter model is straightforward. A two-factor model requires a set of factor loadings multiplying a single random effect. For example, a logit model for the ith subject responding correctly to the jth item (j=1,..,J) is
logit[p(ij)] = a1*item1(i) + ... + aJ * itemJ(i) + lambda1*item1(i)*u(i) + ... + lambdaJ*itemJ(i)*u(i) where the lambdas are factor loadings, with lambda1 fixed to 1.0 and item1-itemJ are dummy variables for the items. Thanks, Dan =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Daniel A. Powers, Ph.D. Department of Sociology University of Texas at Austin 1 University Station A1700 Austin, TX 78712-0118 phone: 512-232-6335 fax: 512-471-1748 [EMAIL PROTECTED] ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
