MCQ Difficulty Index Calculator
This MCQ difficulty index calculator helps educators evaluate how difficult a multiple-choice question is for a group of students. Enter the total number of students, how many answered correctly, and the upper and lower 27% groups to instantly get the difficulty (P) and discrimination (D) indices.
How It Works & Formula
The difficulty index is P = correct / total. A high P value means the item was easy, while a low P means it was hard. The discrimination index is D = (upper - lower) / n27, where n27 is 27% of the total students.
Frequently Asked Questions
What is a good difficulty index?
A P value between 0.30 and 0.70 is generally considered ideal. Values above 0.70 indicate an easy item and below 0.30 a difficult item.
What does the discrimination index tell me?
The D index shows how well a question separates high performers from low performers. A value of 0.40 or above is good, 0.20 to 0.39 is fair, and below 0.20 is poor.
Why use the upper and lower 27%?
Splitting students into the top 27% and bottom 27% is a standard item-analysis technique that maximizes the contrast between high and low scorers.