[R] help R IRT simulation

[Dimitris Rizopoulos]

to simulate from IRT models have a look at function rmvlogis() from 
package ltm.


I hope it helps.

Best,
Dimitris


On 3/3/2010 6:05 PM, Stuart Luppescu wrote:
> 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.

-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

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