[Rasch] On Best Practices for Rasch Scoring
Juanito Talili
talilij at yahoo.com
Tue Sep 20 20:41:21 EST 2011
Recently I wrote:
We are using Rasch model to develop our test questionnaire. The end goal of our tests is to compute scores. Assuming that after Rasch analysis using n=400 students, I arrived a math test questionnaire consisted of 50 items. I will now administer the questionaire to another students (say 200) and then compute the scores for each of the students.
Two scenarios:
Scenario 1: Using n=400, I will save the person measures and item measures, then use such values to compute the scores of the 200 students.
Scenario 2: I will not use any values from the previous analysis. Instead, I will just use the data obtained from the 200 students then run directly the winsteps.
Question: Which scenario is the best practice in using Rasch Analysis?
A third scenario was emailed offlist by somebody, which he think it is the best scenario: He wrote and I quoute:
"The best scenario is the following, I think: Calibration using N=600 (sample A + sample B). This procedure will improve the estimation (good information is always better that less)."
Follow-up question: I think the third scenario says that I have to combined all my data, then pick-up the scores for Sample B. Is the third scenario methodologically sound? Can someone suggest for references regarding the third scenario? My boss always ask for references when I present new things.
Thank you.
Juanito
From: Gerardo Prieto <gprieto at usal.es>
To: talilij at yahoo.com
Sent: Tuesday, September 20, 2011 5:31 PM
Subject: the best scenario
Te best scenario is the following, I think:
Calibration using N=600 (sample A + sample B). This procedure will improve the estimation (good information is always better that less).
Gerardo
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