Re: [R] multilevel factor model in lmer
Dan: lmer cannot currently be used for the 2PL. As you note, it is straightforward to estimate the 1PL, but the a-parameters present a current challenge. Doug mentioned to me the other day he is doing some work on this, so I have copied him on this reply. Harold -Original Message- From: [EMAIL PROTECTED] on behalf of Dan Powers Sent: Sun 10/1/2006 10:15 PM To: 'R-Help' Subject: [R] multilevel factor model in lmer 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] __ R-help@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 and provide commented, minimal, self-contained, reproducible code. [[alternative HTML version deleted]] __ R-help@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 and provide commented, minimal, self-contained, reproducible code.
Re: [R] multilevel factor model in lmer
If you just want to fit the 2PL, without any covariates, then this can be currently handled by function ltm() in package ltm. Best, Dimitris Dimitris Rizopoulos Ph.D. Student Biostatistical Centre School of Public Health Catholic University of Leuven Address: Kapucijnenvoer 35, Leuven, Belgium Tel: +32/(0)16/336899 Fax: +32/(0)16/337015 Web: http://med.kuleuven.be/biostat/ http://www.student.kuleuven.be/~m0390867/dimitris.htm - Original Message - From: Doran, Harold [EMAIL PROTECTED] To: [EMAIL PROTECTED]; R-Help r-help@stat.math.ethz.ch Cc: [EMAIL PROTECTED] Sent: Monday, October 02, 2006 12:22 PM Subject: Re: [R] multilevel factor model in lmer Dan: lmer cannot currently be used for the 2PL. As you note, it is straightforward to estimate the 1PL, but the a-parameters present a current challenge. Doug mentioned to me the other day he is doing some work on this, so I have copied him on this reply. Harold -Original Message- From: [EMAIL PROTECTED] on behalf of Dan Powers Sent: Sun 10/1/2006 10:15 PM To: 'R-Help' Subject: [R] multilevel factor model in lmer 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] __ R-help@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 and provide commented, minimal, self-contained, reproducible code. [[alternative HTML version deleted]] __ R-help@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 and provide commented, minimal, self-contained, reproducible code. Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm __ R-help@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 and provide commented, minimal, self-contained, reproducible code.
Re: [R] multilevel factor model in lmer
Harold and Dimitris -- Thanks very much. Cheers, 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] -Original Message- From: Dimitris Rizopoulos [mailto:[EMAIL PROTECTED] Sent: Monday, October 02, 2006 6:05 AM To: Doran, Harold; [EMAIL PROTECTED]; R-Help Cc: [EMAIL PROTECTED] Subject: Re: [R] multilevel factor model in lmer If you just want to fit the 2PL, without any covariates, then this can be currently handled by function ltm() in package ltm. Best, Dimitris Dimitris Rizopoulos Ph.D. Student Biostatistical Centre School of Public Health Catholic University of Leuven Address: Kapucijnenvoer 35, Leuven, Belgium Tel: +32/(0)16/336899 Fax: +32/(0)16/337015 Web: http://med.kuleuven.be/biostat/ http://www.student.kuleuven.be/~m0390867/dimitris.htm - Original Message - From: Doran, Harold [EMAIL PROTECTED] To: [EMAIL PROTECTED]; R-Help r-help@stat.math.ethz.ch Cc: [EMAIL PROTECTED] Sent: Monday, October 02, 2006 12:22 PM Subject: Re: [R] multilevel factor model in lmer Dan: lmer cannot currently be used for the 2PL. As you note, it is straightforward to estimate the 1PL, but the a-parameters present a current challenge. Doug mentioned to me the other day he is doing some work on this, so I have copied him on this reply. Harold -Original Message- From: [EMAIL PROTECTED] on behalf of Dan Powers Sent: Sun 10/1/2006 10:15 PM To: 'R-Help' Subject: [R] multilevel factor model in lmer 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] __ R-help@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 and provide commented, minimal, self-contained, reproducible code. [[alternative HTML version deleted]] __ R-help@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 and provide commented, minimal, self-contained, reproducible code. Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm __ R-help@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 and provide commented, minimal, self-contained, reproducible code.
[R] multilevel factor model in lmer
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] __ R-help@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 and provide commented, minimal, self-contained, reproducible code.
