[Rasch] Fan

Trevor Bond trevor.bond at jcu.edu.au
Tue Oct 30 20:45:21 EST 2007


Dear Anthony
In Bond & Fox (2007), we spend a couple of pages 
(pp.267-268) addressing the flaws/claims in Fan's 
argument / demonstration . (It follows our 
reflection on Goldstein's infamous "Una Tecnica 
Mafiosa" assertion.)

best wishes
TGB

At 2:37 AM -0700 10/29/07, Anthony James wrote:
>Hi there,
>Fan (1998) argues that item and person 
>statistics based on CTT and IRT are very similar 
>and the complexities of IRT are not worthwhile.
>Has this been reacted to by the Rasch and IRT communities?
>Iâ*™d be thankful for any sources that are brought to my attention.
>
>Is replicating Fanâ*™s research worthwhile?
>
>This is my own view:
>Item and person raw scores are the sufficient 
>statistics in the Rasch model and item and 
>person measures are based on these and highly 
>correlate with raw scores. Therefore, one will 
>always get Fanâ*™s results. What fan hasnâ*™t 
>apparently noticed is the robustness of the 
>person and item measures in the Rasch 
>measurement to the idiocyncracies of the test 
>and sample.
>Heâ*™s arguing on the basis of high correlations 
>(obtained from large and homogeneous groups) 
>which simply mean the rank order of the items 
>and persons remain the same regardless of the 
>testing theory. This can hardly be news.
>S/he defines the high-ability group â*œas those 
>whose scores fall within the 15th and 100th 
>percentile â*¦.low-ability group was defined as 
>those whose scores fall within the 0 to 85th 
>percentile rangeâ*¦â* (p.363). Most of this 
>sampling is shared. They have a lot in common.
>
>Ben Wrightâ*™s 1968 experiment (Memo#1) provides 
>the acid test for the comparison of the two 
>models.
>Cheers
>Anthony
>
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-- 
Trevor G BOND Ph D
Professor and Head of Dept
Educational Psychology, Counselling & Learning Needs
D2-2F-01A EPCL Dept.
Hong Kong Institute of Education
10 Lo Ping Rd, Tai Po
New Territories HONG KONG

Voice: (852) 2948 8473
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