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Education QUESTION #6784
Question 1
A test item reads: 'Which of the following is NOT an example of formative assessment?' with correct answer option 'Final examination'. A student incorrectly answers 'Weekly quiz'. According to item analysis in CTT, if students with high total test scores systematically choose 'weekly quiz' as their answer, what does the discrimination index likely indicate?
  • A high positive D value, indicating the item works well
  • A negative D value, indicating that the item functions in reverse — high achievers are misled while lower achievers answer correctly — suggesting the item needs immediate review✔️
  • A D value near 0, indicating the item has no differential effect
  • A D value above 0.40, indicating excellent item quality
Correct Answer Explanation
If high-scoring students are more likely to answer incorrectly than low-scoring students, the item discrimination index D = (Upper Group % Correct) – (Lower Group % Correct) will be negative. Negative D values are the most serious item analysis warning sign, typically indicating a keying error, ambiguous wording, or a misleading clue that advantageously targets lower-ability guessers over informed higher-ability students.