On Wed, Jul 27, 2011 at 2:58 PM, Erica Crome <erica.cr...@mq.edu.au> wrote: > Afternoon R help, > > I want to run Rasch/IRT analyses using the ltm package, however, I am > using large scale survey data which requires weighting for accurate > results. I attempted to create a weighted object to insert into the > formulae of the ltm packages, however, the survey data only includes > 30 replicate weights and a sampling weight. The svrepdesign requires > additional information such as jacknife weights in an external object > (for scale, rscale), however, I do not have these. I typically just > use the sampling weight when doing analyses in other platforms such as > MPlus, however there does not appear to a way of referring to this > directly in the ltm formulae. > > My question is: am I able to insert sampling weights directly into an > ltm analysis, or is there a way of creating a weighted data object > with the information available which I could then insert into the ltm > analyses? I have been unable to find any similar help topics using the > websearch. Thanks. >
You can easily use svrepdesign() to create a weighted survey design object using the replicate weights, but that won't help you. The functions in the ltm package do not appear to accept any sort of weights. I don't know enough about those models to know if simple weighting would be enough or whether pairwise sampling probabilities would be needed as they are for linear mixed models. -thomas -- Thomas Lumley Professor of Biostatistics University of Auckland ______________________________________________ R-help@r-project.org 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.
