On Wed, 2010-03-03 at 09:45 -0600, Helen Lisman wrote: > 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.
Interesting. I wrote a program in C to simulate item responses according to the Rasch model, as well as the 2PL and 3PL models. I used either normal or uniform distribution of the person and item parameters. I'm assuming that you want to manipulate the skewness and kurtosis of the generated item and/or person parameters, and then produce simulated item responses. I don't know how you would manipulate the skewness and kurtosis. I searched around and rnorm() doesn't include arguments for skewness and kurtosis. kurtosis() functions exist in e1071 and fUtilities, but they only return the kurtosis of the input data. Let me know if you find something. -- Stuart Luppescu <s...@ccsr.uchicago.edu> University of Chicago ______________________________________________ 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.
