[Rasch] How many anchor items do I need

Trevor Bond trevor.bond at jcu.edu.au
Wed Jul 11 10:26:23 EST 2007

Peter and Robert give important advice, but the issue of face 
validity - now dressed up as curricular validity - has always been a 
disturbing aspect of US achievement testing for me.

What indeed are we testing if mere exposure to the items will change 
children's performance on them?

Technically, stable items with a spread of difficulties across the 
latent trait are best - but quality is always better than quantity.

What decisions you may make after the anchoring might be better seen 
as part of Messick's consequential validity. I believe that is the 
issue behind the 'curricular validity' issue - the impact of the 
anchored test results on the kids.


At 4:24 PM -0700 7/10/07, Hendrickson, Peter wrote:
>Content-class: urn:content-classes:message
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>...and even if we had a common curriculum, how would we know that 
>the instruction had a similar degree of commonality?  Our commitment 
>to monitoring fidelity of implementation is honored, for the most 
>part, in the breach. 
>Peter Hendrickson
>Assessment Specialist
>Everett (WA) Public Schools

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
Fax:  (852) 2948 7983
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