Unmeasurable |
This is for 32-bit Facets 3.87. Here is Help for 64-bit Facets 4
If an element is reported as "Unmeasurable" in Table 7 or Status "-4" in a Score file, then ...
Observations for the element are part of an extreme score. One way is to impute non-extreme elements.
For instance:
Original specifications and data:
Models = ?, ?, R5 ; persons, items, rating-scale is 1-5
Data =
1, 1-2, 3, 4
2, 1-2, 3, 2
3, 1-2, 5, 5
4, 1-2. 1, 2
Person 3 is reported as "Unmeasurable". This is because it is the only person element rated 5, and all its ratings are 5. We know that 5 is better than 4, but the data do not tell us how much.
Let's say that 5 is only a little better than 4. Then we impute observations of 4 to Person 3:
Models =
3, ?, RScale, 0.5 ; weight observations of 3 at o.5
?, ?, RScale ; everyone else remains as before
*
Rating-scale = RScale, R5, General ; Person 3 and everyone else share the same rating scale
Data =
1, 1-2, 3, 4
2, 1-2, 3, 2
3, 1-2, 5, 5 ; original data, now weighted 0.5
3, 1-2, 4, 4 ; imputed data, now weighted 0.5
4, 1-2. 1, 2
Person 3 will now be estimated with a measure corresponding to a rating of 4.5
Help for Facets Rasch Measurement and Rasch Analysis Software: www.winsteps.com Author: John Michael Linacre.
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