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What is Item Analysis?

November 18th, 2021

Item analysis is analyzing individual items to make sure that their difficulty level is appropriate, that they discriminate well between students of different performance levels, and then looking deeper into distractor rationales and response frequencies.

Item Difficulty in Item Analysis

So the first thing that we look at in terms of item analysis is item difficulty. Item difficulty is a percentage of students scoring correctly on the item. As a rule of thumb, we’re looking for at least 20% of students scoring correctly on an item. If we have less than 20% of students scoring correctly on the item, that item might be too difficult.

At the same time, if we have more than 80% of students scoring correctly on the item, that item might be too easy. However, in some situations that might be okay. For example, on a mastery test, we can expect a lot of items to be easy, because the students have mastered that material. This is opposed to if we have a pretest, where we can expect most of the items to be somewhat difficult.

Item Discrimination in Item Analysis

The second piece that we look at in terms of item analysis is item discrimination. How well does the item discriminate between students who performed higher and lower? So we look at how well the students scored on the assessment as a whole, and how well the students scored on any given item. Are the students who performed higher scoring correctly on most of the items? Are student who performed lower scoring incorrectly on most of the items?

Response Frequency in Item Analysis

Once we look at item difficulty and item discrimination, and we have cleared potential flags (the item is too difficult or does not discriminate), it’s very important for us to look at the response frequency. For items such as multiple choice, multiple select, or items that have Part A and Part B, it’s really important to look at what responses students are choosing. If they’re not choosing the correct answer, what are some of the distractors they’re choosing and why? Let’s say the correct answer was C but most of the students are choosing B. We need to look at that specific distractor and try to figure out the common misconception. Why are students choosing that particular response?


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