[Rasch] Facets feature or bug?

Purya Baghaei puryabaghaei at gmail.com
Mon Apr 2 18:33:34 EST 2012


Then it guess it should be possible to set the mean difficulty of the
subset of items each marker has been given to zero.

On 4/2/12, Iasonas Lamprianou <liasonas at cytanet.com.cy> wrote:
>
> 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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>> > Rasch at acer.edu.au
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>> >
>>
>>
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-- 
Purya Baghaei, Ph.D
English Department,
Islamic Azad University,
Ostad Yusofi St.
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