Assume that, for a given item, U = L = 10 and 80% of the examinees in the upper group but only 30% of those in the lower group get the item right. Then
A) p = .55, D = -.50.
B) p = .45, D = .60.
C) p = .55, D = .50.
D) p = 1.10, D = .25.

Question

Quizplus · Accepted Answer

The correct answer is calculated using the formulas for p (proportion correct) and D (discrimination index). p = (U + L) / 2 = (80% + 30%) / 2 = 55% or .55. D = U - L = 80% - 30% = 50% or .50.

Assume That, for a Given Item, U = L =