﻿ CATREF= reference category for Table 2

# CATREF= reference category for Table 2 = (item measure)

If a particular category corresponds to a criterion level of performance, choose that category for CATREF=.

Table 2, "most probable responses/scores", maps the items vertically and the most probable responses, expected scores, and Rasch-Thurstone thresholds (50% cumulative probabilities) horizontally. Generally, the vertical ordering is item difficulty measure. If, instead, a particular category is to be used as the reference for sorting, give its value as scored and recoded.

Special uses of CATREF= are:

CATREF=-3 for item entry order

CATREF=-2 for item measure order

CATREF=-1 for items measure order with ISGROUPS=

CATREF=0 for item measure order

CATREF=1...254 for item measure order based on this category.

Example 1: You have 4-point partial-credit items, entered in your data as A,B,C,D, and then scored as 1,2,3,4. You wish to list them based on the challenge of category C, rescored as 3,

CODES =ABCD  ; original responses

NEWSCORE=1234 ; rescored values

RESCORE=2  ; rescore all

CATREF=3  ; Table 2 reference category

ISGROUPS=0  ; partial credit: one item per grouping

If, for an item, the category value "3" is eliminated from the analysis or is the bottom category, the nearest higher category is used for that item.

Example 2: You have 6 3-category items in Grouping 1, and 8 4-category items in Grouping 2. You wish to list them in Table 2.2 by measure within grouping, and then by measure overall.

CODES=1234

NI= 14

ISGROUPS= 11111122222222

TFILE=*

2.2 0 0 0 -1  -1 ; means CATREF=-1

2.2 0 0 0 0  ; last 0 means CATREF=0

*

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Rating Scale Analysis, Wright & Masters Introduction to Rasch Measurement, E. Smith & R. Smith Introduction to Many-Facet Rasch Measurement, Thomas Eckes Invariant Measurement with Raters and Rating Scales: Rasch Models for Rater-Mediated Assessments, George Engelhard, Jr. & Stefanie Wind Statistical Analyses for Language Testers, Rita Green
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