Fitting a multivariate latent trait m... PreviousNext
Mplus Discussion > Latent Variable Mixture Modeling >
 Derek Xu posted on Sunday, March 28, 2010 - 5:46 pm
Hello, I am a beginner and try to fit a multivariate latent trait model in Mplus:

Prob (Y_gki <= c_l | Z_gi, U_gi)
= r_gk + (1 - r_gk)/(1 + exp(-(alpha_kl + beta_k*Z_gi + delta_k*U_gi)))

g = 1,2 indicating groups,
k = 1,..., 7 indicating 7 instrument items,
i indicating the subject number in each group,
so Y_gki is the response for item k from subject i in group g;

each item has a Likert scale with responses 0-5

Z_gi = (Z1_gi, Z2_gi) is 2 dimentional latent variable and assumed to follow bi-variate normal distribution

It's known that Z1 relates to first 3 instrument items and Z2 relates to the other 4 items. So beta_k can be determined.

U_gi is observed covariate.

The parameter of interest is r_gk and its MLE is needed.

May I know if Mplus can fit such a model? If yes, which example/section of handouts/paper shall I follow?

Thanks a lot!!
 Linda K. Muthen posted on Monday, March 29, 2010 - 8:24 am
I think r is a guessing parameter. The current version of Mplus does not estimate a three-parameter IRT model.
 Derek Xu posted on Monday, March 29, 2010 - 10:35 am
Thanks for your response, Linda.

Do you know if there any other approaches to fit such a model?
 Linda K. Muthen posted on Tuesday, March 30, 2010 - 8:29 am
I don't know of any program that includes the guessing parameter and covariates. Check to see if any of the IRT programs put out by Scientific Software can do this.
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