What is discrimination index and its formula?

What is discrimination index and its formula?

The Discrimination Index (D) is computed from equal-sized high and low scoring groups on the test. Subtract the number of successes by the low group on the item from the number of successes by the high group, and divide this difference by the size of a group. The range of this index is +1 to -1.

What is discriminatory index?

The item discrimination index is a measure of how well an item is able to distinguish between examinees who are knowledgeable and those who are not, or between masters and non-masters. A negative discrimination index may indicate that the item is measuring something other than what the rest of the test is measuring.

What is the discrimination index quizlet?

discrimination index This statistic represents the simple correlation between the score on an item and the total test score.

What is item difficulty and item discrimination?

So item difficulty helps us to know the degree to which students get answers correct, whereas item discrimination examines how the top-scoring group of test takers compares to the lowest-scoring group of test takers, another important piece of information to help us know how well our items are working.

What does a positive discrimination index indicate?

Optimally an item should have a positive discrimination index of at least 0.2, which indicates that high scorers have a high probability of answering correctly and low scorers have a low probability of answering correctly.

What are the two decisions to be made in deciding how do you score an index?

What are the two decisions to be made in deciding how to score an index? The desirable range of index scores and the assignment of scores for each response.

What is the discrimination index for item 1?

In the example above – item 1 has a mean of 60% i.e. 60% of all students got it right. It also has a good Discrimination Index (DI) of 0.4 meaning that this item could be used as a ranking question to help separate the stronger from the weaker candidates.

What is the difference between discrimination and difficulty index?

It is the difference between the proportion of the top scorers who got an item correct and the proportion of the bottom scorers who got the item right 12. The discrimination index range is between -1 and +1 13. The closer the index is to +1, the more effectively the item distinguishes between the two groups of students 14.

What is the mean discrimination index of McQ?

In this, it shows that 75% had discrimination index of more than 0.2. Out of 75%, 65% showed mean discrimination index of equal to or more than 0.4, indicating that these MCQ item were excellent test items for differentiating between poor and good performers. There were no items with negative discrimination index.

How do you calculate the discrimination index in Excel?

You then take the number of candidates from the lower group who got the item correct away from the number of candidates from the upper group who got the item correct, divide by the number of candidates in a group, and you will get a number between -1 and 1. This is the discrimination index for the item.