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Education QUESTION #6756
Question 1
A teacher constructs a test and finds that item discrimination index D = -0.15 for question 7. Which interpretation is MOST accurate?
  • High-ability students found the item tricky, indicating it is a good challenging item
  • Students in the lower-scoring group performed better on this item than students in the upper-scoring group — the item is likely flawed and should be removed or revised✔️
  • The item is too easy and should be made more difficult to improve discrimination
  • A negative D value is acceptable as long as the item p-value is above 0.50
Correct Answer Explanation
The discrimination index D = (Upper Group % Correct) – (Lower Group % Correct). A negative D means the lower-scoring group outperformed the upper-scoring group on this item. This is a serious red flag: it could indicate a keying error, ambiguous wording, or content that rewards lower-ability guessers. Such items should be removed from scoring or revised.