Hello,
Thank you very much for the tip. I think that the irt.ability() function is
what I'm looking for but I'm not sure.
To be more clear, I have obtained item parameters from the LLTM function in
the eRm package which allows for repeated measurements. I have 10 items
measured at 2 time points, for a total of 20 item parameters. I wish to get
the ability estimate for a person at time 1 and then separately at time 2.
Here is the code I'm using but it doesn't seem to work.
ItemParams<-c(-0.199,-0.283,0.109 ,0.142 ,0.056
,-0.062,-0.125,0.066,0.153,0.142,
0.102,0.019,0.411,0.443,0.357,0.239,0.176,0.368,0.454,0.443)
Time1Params<-list("1pl" = list (b = ItemParams[1:10]))
Time2Params<-list("1pl" = list (b = ItemParams[10:20]))
irt.ability(c(1,0,1,1,1,1,0,1,1,1),Time1Params,method="MLE")
irt.ability(c(1,1,1,1,0,0,1,1,1,1),Time2Params,method="MLE")
Also, I've tried to locate the MP Vignette but have been unsuccessful.
Thanks again for your timely response. It's greatly appreciated!
Best,
Kim
Doran, Harold wrote:
>
> 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-boun...@r-project.org
>> [mailto:r-help-boun...@r-project.org] On Behalf Of Tessari
>> Sent: Wednesday, September 02, 2009 11:50 AM
>> To: r-help@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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>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
> ______________________________________________
> R-help@r-project.org mailing list
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> PLEASE do read the posting guide
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> and provide commented, minimal, self-contained, reproducible code.
>
>
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View this message in context:
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Sent from the R help mailing list archive at Nabble.com.
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