[Rasch] Facets feature or bug?

Iasonas Lamprianou liasonas at cytanet.com.cy
Mon Apr 2 18:11:51 EST 2012

thank you Trevor

i am afraid that i only have your edition one of the book, can i find this information there as well? also i apologise for not understanding fully your position so i need a clarification. your position is that it is not a bug and facets can recover some useful info to compare the raters although no double marking of any magnitude exists. am i missing something?

----- Original Message Follows -----
From: "Bond, Trevor" <trevor.bond at jcu.edu.au>
To: "rasch at acer.edu.au" <rasch at acer.edu.au>
Subject: Re: [Rasch] Facets feature or bug?
Date: Mon, 2 Apr 2012 00:30:29 -0700
> Jason, I think this covers it:
> Linacre (1997) displayed three judging rosters for ratings from the Advanced
> Placement Program of the College Board. The complete judging plan of 1,152
> ratings illustrates the ideal plan for both conventional and Rasch analysis.
> This complete judging plan meets the connection requirement between all
> facets because every element (essays, examinees, and judges) can be compared
> directly and unambiguously with every other element.
> A much less judge-intensive plan of only 180 ratings also is displayed, in
> which less precise Rasch estimates can be obtained because the facet-linking
> overlap is maintained. The Rasch measures would be less precise than with
> complete data because 83% fewer observations are made. LinacreΉs final table
> reveals the minimal judging plan, in which each of the 32 examineesΉ three
> essays is rated by only one judge. Each of the 12 judges rates eight essays,
> including two or three of each essay type, so that the examinee­judge essay
> overlap of these 96 ratings still enables all parameters to be estimated
> unambiguously in one frame of reference.
> Of course, the saving in judgesΉ costs needs to be balanced against the cost
> of low measurement precision, but this plan requires only 96 ratings, 8% of
> the observations required for the complete judging plan. Lunz et al. (1998)
> reported the successful implementation of such a minimal judging plan
> (Linacre, 1997).
> B&F 2 p149
> On 2/04/12 4:53 PM, "Iasonas Lamprianou" <liasonas at cytanet.com.cy> wrote:
> > 
> > Dear all,
> > I send this question to all, and not only to Mike, because this question is
> > both related to the Facets software, but is a methodological question as well.
> > 
> > I am running a "typical" scenario where I have markers who mark the responses
> > of students to a test. The markers do not see the whole test, but only
> > individual questions. We do NOT have double marking. So, lets say that we have
> > 1000 students, each one responding to 10 questions. In effect, we have 10.000
> > responses. Lets say that each one of the 10.000 responses is randomly sent
> > once to one marker. We have 20 markers in total.
> > 
> > Observation 1: the 3-d matrix markersXitemsXstudents is VERY sparse (we will
> > all agree on that) because we have NO double marking
> > Observation 2 which is a question as well: I think that the design is NOT
> > linked (no double marking), does everyone agree? However, Facets does not
> > complain about disconnected subsets, I do not know why. Should I not worry?
> > Does Facets assume that because of randomness, all markers are on the same
> > scale? Is Facets confused and incorrectly thinks that the design is NOT
> > disconnected?
> > 
> > Question: If disconnected subsets is a problem in this case, how can I run an
> > anlysis in order to identify marker effects using this dataset?
> > 
> > Thank you for your help
> > 
> > Jason
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