A five-item ability test was administered to a group of 100 students. The items

Question

A five-item ability test was administered to a group of 100 students. The items were in multiple-choice format with five options and among them, one is the correct choice and four are distractors. Subjects' overall performances were then classified into one of the three ability groups. Specifically, the high group (H) consisted of the top 30 students whereas the low group (L) consisted of the bottom 30 students. The remaining were in the middle group (M). The table below shows the counts of correct response on each item by the three performance groups: a. For each item, compute the difficulty index, the difficulty index controlled for guessing, and the discriminability index. b. Make a D-D (difficulty vs. discriminability) plot and decide which items should be retained.

Explanation / Answer

Item h m l total correct guesses difficulty index discrimination index 1 13 7 5 26 9.59% 5.83% 7.77% 2.47% 2 20 23 27 72 26.57% -2.91% -6.80% -4.94% 3 22 19 15 59 21.77% 2.91% 6.80% 4.94% 4 19 17 15 55 20.30% 1.94% 3.88% 2.47% 5 29 15 10 59 21.77% 13.59% 18.45% 6.17%

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