

IRT EAP scores and missing data 

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Hi Drs. Muthen, When estimating the value of theta (ability) from an IRT model using the Expected A Posteriori method, how does Mplus handle records with missing values for 1 or more items? Does it simply use the remaining nonmissing items? Is there a proportion for missing items above which it does not make sense to calculate theta (e.g., 50%)? In case it is important, I am using a 2parameter logistic IRT model with binary items. Thanks! 


Q1. The parameter estimation uses all available data with ML assuming MAR. The ability (factor score) estimation uses the subject's nonmissing items. Q2. That's difficult to say but you do get a SE for the factor score estimate for the person so that can tell you about lack of precision. 

Weizi Wang posted on Monday, June 12, 2017  4:04 am



Hi, I am wondering how to estimate the theta (ability) using Mplus. Is it the factor score output by the program the estimate of the theta? If so, I am wondering how to output all the factor scores since they are not outputted completely by default. 


Yes, the factor scores are the theta estimates. Use the Savedata command and the option Save=fscores. 

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