[Rasch] Fan: raw scores and Rasch

Jim Athanasou Jim.Athanasou at uts.edu.au
Tue Oct 30 11:44:10 EST 2007

Mike or other colleagues:

Does anyone have a small (or large) dataset that can be used to show 
these differences (a) for missing data; and (b) for floor or ceiling 
effects. This would be helpful for teaching purposes.

Please do not worry if it is not possible or convneient at this time.

Kind regards,
Jim Athanasou

Mike Linacre (RMT) wrote:

> Quote: "There simply is little appreciable difference between raw 
> score sums and the Rasch model,"
> Except when there is an appreciable difference!
> For instance, when there is missing data ...
> Or when the floor and ceiling effects of raw score sums are producing 
> misleading inferences. In one study, a raw-score "ceiling effect" was 
> being misunderstood as "the therapy has stopped being cost-effective". 
> In fact, the therapy was increasingly cost-effective.
> Or when instruments must be equated. Even the great statistician, John 
> Tukey, misequated samples based on raw-score-percentages, producing 
> nonsense results: www.rasch.org/rmt/rmt64m.htm
> <http://www.rasch.org/rmt/rmt64m.htm>Mike L.
> Mike Linacre
> Editor, Rasch Measurement Transactions
> rmt at rasch.org www.rasch.org/rmt/ <http://www.rasch.org/rmt/> Latest 
> RMT:  21:1 Summer 2007
>Rasch mailing list
>Rasch at acer.edu.au


James A Athanasou PhD, MAPS
Associate Professor
Faculty of Education
University of Technology, Sydney
PO Box 123, Broadway 2007
Tel. +61-2-9514-3712 Fax. +61-2-9514-3939


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