(controlled by T2SELECT=, MRANGE=, CATREF=)
Table 2 for multiple-choice items.
Table 2 for polytomous items.
Multiple-choice items
Table 2.14 shows the item difficulties (or more generally the Rasch-Andrich thresholds) coded by the option of the higher category. For item "al07" this is "d", the correct option.
TABLE 2.4 STRUCTURE MEASURES (Rasch model parameters: equal-adjacent-probability thresholds) (ILLUSTRATED BY AN OBSERVED CATEGORY)
-4 -3 -2 -1 0 1 2 3 4
|------+------+------+------+------+------+------+------| NUM TOPIC
| d | 55 al07 newspaper
| c | 64 sa01 magazine
Table 2.14 is the same as Table 4, the Rasch-Andrich thresholds, but the options are shown by their scored values, not by their codes in the data.
TABLE 2.14 STRUCTURE MEASURES (Rasch model parameters: equal-adjacent-probability thresholds) (BY CATEGORY SCORE)
-4 -3 -2 -1 0 1 2 3 4
|------+------+------+------+------+------+------+------| NUM TOPIC
| 1 | 55 al07 newspaper
| 1 | 64 sa01 magazine
Polytomous items
Tables 2.4 & 2.14 show Rasch structure calibrations: Rasch-Andrich thresholds (step parameters, step measures, step difficulties, rating (or partial credit) scale calibrations). These are the relationships between adjacent categories, and correspond to the points where adjacent category probability curves cross, i.e., are equally probable of being observed according to a Rasch model.
STRUCTURE MEASURES (Rasch model parameters: equal-adjacent-probability Rasch-Andrich thresholds) (BY CATEGORY SCORE)
-6 -4 -2 0 2 4 6
|---------+---------+---------+---------+---------+---------| NUM ACT
| 1 2 | 5 FIND BOTTLES AND CANS
| |
| 1 2 | 23 WATCH A RAT
| 1 2 | 18 GO ON PICNIC
|---------+---------+---------+---------+---------+---------| NUM ACT
-6 -4 -2 0 2 4 6
1
12 2 2117083563422342 111 1 1 1 1 KID
T S M S T
0 10 30 50 70 80 90 99 PERCENTILE
