(controlled by T2SELECT=, MRANGE=, CATREF=)
Table 2 for multiple-choice items.
Table 2 for polytomous items.
Multiple-choice items
Table 2.13 shows the 50% cumulative probability points, the Rasch-Thurstonian thresholds. The lower category ("a" and other wrong answers) has a greater than 50% probability of being observed up to 3.2 logits, when "d", the correct answer, has a higher than 50% probability.
TABLE 2.3 50% CUMULATIVE PROBABILITY (Rasch-Thurstonian THRESHOLD) (ILLUSTRATED BY AN OBSERVED CATEGORY)
-4 -3 -2 -1 0 1 2 3 4
|------+------+------+------+------+------+------+------| NUM TOPIC
a d d 55 al07 newspaper
a c c 64 sa01 magazine
Table 2.13 is the same as Table 2.3, but the options are shown by their scored values, not by their codes in the data.
TABLE 2.13 50% CUMULATIVE PROBABILITY (Rasch-Thurstonian THRESHOLD) (BY CATEGORY SCORE)
-4 -3 -2 -1 0 1 2 3 4
|------+------+------+------+------+------+------+------| NUM TOPIC
0 1 1 55 al07 newspaper
0 1 1 64 sa01 magazine
Polytomous items
Tables 2.3 & 2.13: The "Cumulative Probability" Table: Rasch-Thurstonian thresholds, selected with CURVES=001, answers the question "whereabouts in the category ordering is a person of a particular measure located?" This information is expressed in terms of median cumulative probabilities (the point at which the probability of scoring in or above the category is .5).
50% CUMULATIVE PROBABILITY: MEDIAN (equal-cumulative-probability Rasch-Thurstonian thresholds) (BY CATEGORY SCORE)
-6 -4 -2 0 2 4 6
|---------+---------+---------+---------+---------+---------| NUM ACT
0 1 2 2 5 FIND BOTTLES AND CANS
| |
0 1 2 2 23 WATCH A RAT
| |
0 1 2 2 20 WATCH BUGS
0 1 2 2 4 WATCH GRASS CHANGE
0 1 2 2 8 LOOK IN SIDEWALK CRACKS
| |
0 1 2 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
