Hierarchical IRT model PreviousNext
Mplus Discussion > Growth Modeling of Longitudinal Data >
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 Chun Wang posted on Friday, August 02, 2013 - 1:09 am
We are trying to estimate parameters of a hierarchical IRT model in Mplus as follows:

th_{ikt} = lamb * th_{i0t} + e1_{ikt}
th_{ikt} ~ item_{1, ikt} ... item_{J, ikt}


We tried the following code:
...
VARIABLE: NAMES ARE it1-it40;
CATEGORICAL ARE it1-it40;
ANALYSIS: TYPE = GENERAL;
ESTIMATOR = MLR;
LINK = LOGIT;
MODEL: th1 BY it1-it20* (p1-p20);
th2 BY it21-it40* (p21-p40);
th0 BY th1-th2* (lamb);
th1-th2@.5
[th1-th2@0];
[th0@0]; th0@1;
....

But constraining [th0@0] and th0@1 is not what we want! We want to freely estimate those parameters while constraining mean(threshold) = 0, var
(threshold) = 1, and th1-th2@*.5 (ev) such that ev = 1-lamb^2 (i.e., constrain the residual variance).

We tried adding a model constraint line for the latter:

MODEL: th1-th2@*.5 (ev);
MODEL CONSTRAINT: ev = 1-lamb^2;

but Mplus complained and forced all of the item loadings to be 1. We would appreciate if you could give us some advice on this issue.
 Bengt O. Muthen posted on Friday, August 02, 2013 - 2:13 pm
Please send input, output, data, and license number to support.
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