R help - Sep 2009 - Ability Estimates for Repeated Measurements in the eRm Package

Dear R Users, 

I am using the LLTM and the LRSM functions in the eRm package to do repeated
measurements where there are 2 measurement points for a list of 10 items.  I
am trying to get ability estimates but am having trouble.  I don't think
that it is appropriate to use the pmat function since the person parameters
are based on all 20 items.  Rather, I think it would be more appropriate to
have the person parameters be based on the 10 items at Time 1 and then the
next 10 items at Time 2.  However, I don't want to form 2 separate Rasch
models since I think it's important to have all 20 item parameters
calculated at once.

Any advice would be greatly appreciated.  Also, if more information is
needed, I could send my sample code.

Best,

Kim
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Not sure I completely understand what you want. You might try looking at
the irt.ability() function in the MiscPscyho package for ability
estimates.
> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Tessari
> Sent: Wednesday, September 02, 2009 11:50 AM
> To: r-help at r-project.org
> Subject: [R] Ability Estimates for Repeated Measurements in 
> the eRm Package
> 
> 
> Dear R Users, 
> 
> I am using the LLTM and the LRSM functions in the eRm package 
> to do repeated measurements where there are 2 measurement 
> points for a list of 10 items.  I am trying to get ability 
> estimates but am having trouble.  I don't think that it is 
> appropriate to use the pmat function since the person 
> parameters are based on all 20 items.  Rather, I think it 
> would be more appropriate to have the person parameters be 
> based on the 10 items at Time 1 and then the next 10 items at 
> Time 2.  However, I don't want to form 2 separate Rasch 
> models since I think it's important to have all 20 item 
> parameters calculated at once.
> 
> Any advice would be greatly appreciated.  Also, if more 
> information is needed, I could send my sample code.
> 
> Best,
> 
> Kim
> --
> View this message in context: 
> http://www.nabble.com/Ability-Estimates-for-Repeated-Measureme
nts-in-the-eRm-Package-tp25260278p25260278.html
> Sent from the R help mailing list archive at Nabble.com.
> 
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