Some discrimination parameters equal ... PreviousNext
Mplus Discussion > Confirmatory Factor Analysis >
Message/Author
 Evgenia  posted on Monday, May 09, 2011 - 7:37 am
How can I set equal discrimination parameters for only some of my items in a 2 parameter IRT model?
If I have a 5 items and Rasch model(all discrimination parameters equal) I have

Model:

f by u1-u5* (1);
f@1;

Now I want only u1:u3 to be equal the other two discimination parameters to be freely estimated

Thanks
 Linda K. Muthen posted on Monday, May 09, 2011 - 12:11 pm
Is this what you mean:

f BY u1* (1)
u2
u3 (1)
u4;
 Evgenia  posted on Monday, May 09, 2011 - 12:30 pm
When I wrote u1:u3 I mean u1=u2=u3
but after your reply I manage to write exactly what I want as
MODEL:f BY u1* (1)
u2(1)
u3(1)
u4
u5; !only b1-b2-b3 equal
f@1;
Thanks alot
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