[Rasch] Threshol Disordering

Mike Linacre (RMT) rmt at rasch.org
Tue Dec 19 00:50:32 EST 2006


Dear Anthony et al.:

Reversed Rasch-Andrich thresholds indicate low probabilities of 
intermediate categories. These usually correspond to relatively low 
frequencies of those categories in the data. So, in your items, some of the 
26 categories (item scores of 0-25) have relatively low frequencies.
If you examine the right-wrong scoring patterns across the missing words 
within each item, it is likely that some patterns are much more frequent 
than others, indicating dependencies among those missing words. These 
dependencies lead to item scores with higher and lower frequencies, and so 
to reversed thresholds.

Mike L.


At 12/18/2006, you wrote:

>Dear List members,
>   I'd be thankful for your expert comments on this.
>   I have Rasch analysed a language test which is called the “cloze
>test”. It has the following form:
>
>   “The English language today _____ many distinct centres,
>self-governing ____ with their own standards. The two ____ important are, 
>of ____,
>the United Kingdom in terms of ____, and the United States in ____ of
>population. 

.”
>
>   The students are to supply the missing words in the text. There are 4
>texts and each have 25 gaps.
>   I have used rating scale model. Each text is a polytomous item with
>25 categories.
>   There is disordering in the thresholds of the test (but not in the
>average measures).
>   How can this be interpreted in the context of a cloze test?
>   Thanks in adavnce
>   Anthony

Mike Linacre
Editor, Rasch Measurement Transactions
rmt at rasch.org www.rasch.org/rmt/ Latest RMT:  20:2 Autumn
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