FAA Fundamentals of Instructing (FOI)The Teaching Process and MethodsMedium
A ground instructor reviews results from a private pilot knowledge test and finds that 85 percent of the students who took the test answered a particular question correctly. This percentage best represents the question's
- Adiscrimination index
- Bitem difficulty index
- Creliability coefficient
- Dcontent validity
Show answer & explanationAnswer & explanation
Correct answer: B. item difficulty index
The item difficulty index is the percentage of examinees who answer a test item correctly, used to determine whether a question is too easy, too hard, or appropriately challenging. Reliability and validity describe overall test qualities, while the discrimination index measures how well an item distinguishes high- from low-scoring students.
Why the other options are wrong
- A. Discrimination index measures how well an item separates strong from weak performers, not overall percent correct.
- C. Reliability refers to the consistency of test results, not the percentage correct on one item.
- D. Content validity relates to whether the test measures the intended subject matter, not a percentage score.
Item Difficulty Index
A statistic representing the percentage of examinees who correctly answer a given test item, used to evaluate whether the item is appropriately challenging.
- Expressed as a percentage of correct responses
- High percentage = easy item; low percentage = difficult item
- Used with the discrimination index to refine test items
Memory trick: Difficulty index = 'Did most get it right?' percentage.