08-23-2016
joseph0
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08-08-2016
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Latest posts by joseph0
Subject Views Posted 2053 08-23-2016 10:48 AM 2070 08-22-2016 02:10 PM 2458 08-20-2016 07:48 PM 2464 08-20-2016 07:28 PM -
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- Got a Like for Re: PROC IRT for polytomous items. 08-23-2016 11:10 AM
- Posted Re: PROC IRT for polytomous items on Statistical Procedures. 08-23-2016 10:48 AM
- Posted PROC IRT for polytomous items on Statistical Procedures. 08-22-2016 02:10 PM
- Got a Like for The Generalized Partial Credit Model in PROC IRT. 08-22-2016 09:47 AM
- Posted Re: The Generalized Partial Credit Model in PROC IRT on Statistical Procedures. 08-20-2016 07:48 PM
- Posted The Generalized Partial Credit Model in PROC IRT on Statistical Procedures. 08-20-2016 07:28 PM
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Subject Likes Posted 2 08-23-2016 10:48 AM 2 08-20-2016 07:28 PM
08-23-2016
10:48 AM
2 Likes
Yes indeed, I must apologize. There was a mismatch between the software I had installed (SAS 9.4, SAS/STAT 13.1) and the newer (SAS 9.4, SAS/STAT 14.1) documentation. I have since updated the software to 14.1. After re-checking the 14.1 documentation, I still don't see a MODEL RESFUNC option for the Generalized Partial Credit Model, although this model is mentioned several other places in the documentation. Though not specifically documented, RESFUNC=GPC works to obtain the Generalized Partial Credit Model in PROC IRT 14.1. As far as the Nominal Response Model is concerned, specifying RESFUNC=NOMINAL in 14.1 (correctly) returns an error in the log, rather than truncated output as in 13.1.
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08-22-2016
02:10 PM
Of the three polytomous item IRT models PROC IRT claims to estimate, it appears that only one (the Graded Response Model) actually works. Recognizing that the procedure is still experimental, there seems no way to even specify the Generalized Partial Credit Model, contrary to information in the documentation. The Nominal Response Model provides some basic preliminary output, including a notice that the convergence criterion has been satisfied, and occasionally the following warning: WARNING: Standard errors for some parameter estimates are close to zero. However, fit statistics and parameter estimates are never produced. Has this been your experience, too?
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08-20-2016
07:48 PM
The only RESFUNC option for ordinal items is GRADED for the Graded Response Model. There is nothing for the Generalized Partial Credit Model.
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08-20-2016
07:28 PM
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Is the Generalized Partial Credit really available in PROC IRT? What’s New in SAS/STAT 14.1 states that The generalized partial credit (GPC) model is available for ordinal items The Response Models part of the Details section states that PROC IRT supports several response models for binary and ordinal responses, and it allows different items to have different response models. Details about these response models and their relationships follow: ... •Generalized partial credit model: This model assumes that items are ordinal-categorical with at most 19 levels. The slopes (or discrimination) and the step parameters of the items are free parameters in the model. In addition, the EQUALITY subcommand includes the following possible specifications: ... _ALLGPC_ _ALLGPCITEM_ specifies all variables that are fitted by the generalized partial credit model in the analysis. ... _ALLGPC_BUT_ [ excluded-variables ] _ALLGPCITEM_BUT_ [ excluded-variables ] specifies all variables except the excluded-variables that are fitted by the generalized partial credit model in the analysis. However, a corresponding RESFUNC= option fof the model is not included in the syntax documentation for the MODEL subcommand. Are these all documenatation errors?
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