[R] Using item difficulties from a fitted Partial Credit Model to predict person abilities in an extended dataset?

Bert Gunter bgunter@4567 @end|ng |rom gm@||@com
Sun Jun 7 17:15:21 CEST 2020

Such package/methodology specific questions may well go unanswered here.
They are essentially offtopic anyway: this list is about general R
programming questions and cannot be expected to support the ~ 20000
packages now in the ecosystem. I suggest that you contact the package
maintainer (?maintainer) for help or to find out what support resources may
be available.

Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

On Sun, Jun 7, 2020 at 3:59 AM Rob Forsyth <rob.forsyth using newcastle.ac.uk>

> I am using the eRm package to examine the properties of a clinical rating
> scale using a Partial Credit Model (PCM). I understand how to extract the
> person ability estimates (thetas) from a simple fitted PCM but I have a
> dataset with repeated observations over time (~1200 observations of the
> instrument in ~250 individuals). So as not to violate assumptions of
> conditional independence I've fitted the PCM to single observations drawn
> at random from each subject. This works but I would now like to use the
> item diffculty estimates from the fitted PCM to generate person-ability
> estimates for the remaining ~950 observations (at other timepoints) not
> used to fit the model; and I can't see from the eRm package documentation
> how to do this?
> Advice very much appreciated
> Rob
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