search for: 2pl

Dear R-List, to assess the model fit for 2PL-models, I tried to mimic the bootstrap-approach chosen in the GoF.rasch()-function. Not being a statistician, I was wondering whether the following simplification (omit the "chi-squared-expressed model fit-step") would be appropriate: GoF.ltm <- function(object, B = 50, ...){ liFits...

Hello All, I was wondering how I can get the overall Pearson chi^2 test of model fit with its df and p value in the LTM package for the 2PL models. Thanks, -- Davood Tofighi Department of Psychology Arizona State University [[alternative HTML version deleted]]

Hi, I'm trying to convert Matrix into a list format and have written the following code: path = ("C:/2PL_Alpha_C_2PL_Loading") setwd(path) getwd() congeneric = matrix(rep(NA,36),nrow=6,ncol=6) conFirst = matrix(rep(NA,36),nrow=6,ncol=6) conFirstTwenty = rep(NA, 20) k = 1 #Reading all the Alpha and Congeneric 2PL values into variables alpha <- read.table("2PLAlphaGenPars_1.dat", h...

The function factor.scores is used with package ltm and others to estimate IRT type scores for various models. It inherits objects of class grm, gpcm and a few others. What I would like to do is to use the factor.scores function, but feed it my own item parameters (from a bifactor model where the 2PL parameters are adjusted for the bifactor structure). Does anybody have an idea of how this might be done? I can, of course, create a list, matrix or other object containing the item parameters, but factor.scores only inherits particular object classes. Any thoughts would be great. Thanks, Jimmy...

I have just submitted irtoys_0.1.0, a package potentially useful for those working with IRT models. It can fit the 1PL, 2PL, and 3PL models through a simple and unified syntax, using either the R package ltm, Brad Hanson's ICL program, or the commercially available BILOG-MG. The purpose is basically to facilitate teaching, and especially comparisons across models and/or programs. Various graphs, item fit statist...

...ng various smoothers (such as Tukey, loess, or kernel). 'ask': interactive turning over of plots can be switched off (only useful if automated figure export is in effect, e.g., when using Sweave). - simulation module for 0-1 response matrices: sim.rasch() for Rasch homogeneous data, sim.2pl() for 2-PL data, sim.xdim() for unidimensionality violation, and sim.locdep() for locally dependent item responses. - package vignette "eRmvig" added. Best, Patrick _______________________________________________ R-packages mailing list R-packages at r-project.org https://stat.ethz.ch/...

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 *

I have just submitted irtoys_0.1.0, a package potentially useful for those working with IRT models. It can fit the 1PL, 2PL, and 3PL models through a simple and unified syntax, using either the R package ltm, Brad Hanson's ICL program, or the commercially available BILOG-MG. The purpose is basically to facilitate teaching, and especially comparisons across models and/or programs. Various graphs, item fit statist...

...ng various smoothers (such as Tukey, loess, or kernel). 'ask': interactive turning over of plots can be switched off (only useful if automated figure export is in effect, e.g., when using Sweave). - simulation module for 0-1 response matrices: sim.rasch() for Rasch homogeneous data, sim.2pl() for 2-PL data, sim.xdim() for unidimensionality violation, and sim.locdep() for locally dependent item responses. - package vignette "eRmvig" added. Best, Patrick _______________________________________________ R-packages mailing list R-packages at r-project.org https://stat.ethz.ch/...

...ics (e.g., item information and test information functions) 3) Various "Classical" statistics for item analysis 4) Coefficient alpha 5) Score conversion tables 6) Classification consistency analysis 7) Procedures for linking scales using mean equating Future development will include * 2PL, 3PL, and GPCM also using JML * Stocking-Lord procedure * Various methods for assessing DIF, including MH * Bayesian scoring methods (e.g., EAP) The JML procedure is not the world's best technology as MML is commonly preferred. However, that is already implemented in the ltm package and these...

hello R, This is about simulation in psychomtrics in IRT in R. I want to simulate b parameters(item difficulty) with moments of fixed values of mean, st.d, skewness and kurtosis. Is there any specific IRT package in R with those functions to control those moments? I have seen other programs that can control mean and st.d but not skewness and kurtosis. Thank you, helen L [[alternative HTML

Hi Everybody, I have just been introduced to R and have used the ltm package for calibrating items under IRT. I have been able to get the item parameters using the fit function under different models. I am using the 2PL model. I have got the parameters for some 300 items from 15 different tests using the function fit. Now I need to automatically generate tests such that they have atleast a certain level of information. Thus I have created a data frame with item id, and information at 20 different points/ability l...

Hi everyone, I am having a bit of trouble correctly structuring an equation in R. Here is the equation Here is what I thought for(i in 1:numItem)for(x in 1:numCat) Ptheta[,i,x]<-(exp(-1.702*a[i]*(theta-b[i,x+1])) My problem is that I am not sure how to get it to read the equation as having two indexing points (i and x). Right now it is trying to read it as a matrix, but

...cored dichotomously, so I think the problem is slightly more complex in this scenario and requires the use of both functions. Last, and a bit tangentially, it is possible when maximizing the 3PL that I will converge upon a local and not global maximum, a situation that does not occur with Rasch or 2PL. I only know of two methods for knowing whether I converged upon the right max. First, plot the likelihood and look at it or second, use different starting points and see if I converge to the same max. However, I am maximizing this likelihood over 80,000 students (or so) and I don't think eithe...

...t version of the package plink has been uploaded to CRAN. plink is a package for conducting unidimensional IRT scaling and chain linking for multiple groups for single-format or mixed-format common items. The package supports eight IRT models and four calibration methods. Dichotomous Models: 1PL, 2PL, 3PL Polytomous Models: -Graded response model -Partial credit model -Generalized partial credit model -Nominal response model -Multiple-choice model Calibration Methods: -Mean/Mean -Mean/Sigma -Haebara -Stocking-Lord Any combination of dichotomous and polytomous items can be supplied with inter...

...t version of the package plink has been uploaded to CRAN. plink is a package for conducting unidimensional IRT scaling and chain linking for multiple groups for single-format or mixed-format common items. The package supports eight IRT models and four calibration methods. Dichotomous Models: 1PL, 2PL, 3PL Polytomous Models: -Graded response model -Partial credit model -Generalized partial credit model -Nominal response model -Multiple-choice model Calibration Methods: -Mean/Mean -Mean/Sigma -Haebara -Stocking-Lord Any combination of dichotomous and polytomous items can be supplied with inter...

...ods. plink is a package for conducting unidimensional and multidimensional IRT-based test linking using separate calibration methods for multiple groups for single-format or mixed-format common items. The package supports sixteen IRT models and eleven calibration methods. Dichotomous Models: 1PL, 2PL, 3PL, M1PL, M2PL, M3PL Polytomous Models: -Graded response model, MD graded response model -Partial credit model, MD partial credit model -Generalized partial credit model, MD generalized partial credit model -Nominal response model, MD nominal response model -Multiple-choice model, MD multiple-ch...

...ods. plink is a package for conducting unidimensional and multidimensional IRT-based test linking using separate calibration methods for multiple groups for single-format or mixed-format common items. The package supports sixteen IRT models and eleven calibration methods. Dichotomous Models: 1PL, 2PL, 3PL, M1PL, M2PL, M3PL Polytomous Models: -Graded response model, MD graded response model -Partial credit model, MD partial credit model -Generalized partial credit model, MD generalized partial credit model -Nominal response model, MD nominal response model -Multiple-choice model, MD multiple-ch...

...013>, Ya-Hui Su and Wen-Chung Wang An example of this is provided in the paper above. They use SAS PROC NLMIXED, and estimate all possible binary and Polytomous IRT models. I want to replicate what they did using R and nlme package. I am able to fit rasch model, but have some error messages for 2PL IRT model. So, I could not go beyond that. This is really important for me, because any nonlinear model can be fitted by using this approach. I would like to see how well nlme() package recovers true parameters, not just regular IRT models but also some other less used IRT models. Here is the exa...

...tp://lists.samba.org/pipermail/samba/ Dear all, is it possible to mount Windoze-shares under Solaris 8 using smbmount (or whatever)? how? Thanks in advance! Martin -- Martin Mielke martin@people-com.com http://www.ydilo.com/ People Communications Tel: +34 91 3447028 P: de la Castellana 216-2pl Systems Department Fax: +34 91 3447059 E-28046 Madrid | Spain [ echo "\$0&\$0">_;chmod +x _;./_ ] Return-Path: <gfk@logidac.com> Delivered-To: samba@lists.samba.org Received: from VL-MS-MR003.sc1.videotron.ca (relais.videotron.ca [24.201.245.36]) b...