Discrimination: Indicates how well a question differentiates between students who know the subject matter and those who don't. A question is a good discriminator when students who answer the question correctly also do well on the test. Values can range from -1.0 to +1.0.
Discrimination Index - The discrimination index is a basic measure of the validity of an item. It is a measure of an item's ability to discriminate between those who scored high on the total test and those who scored low.
How to Run an Item Analysis on a Test:Go to one of the previously listed locations to access item analysis (see above).Access the test's contextual menu from the downward facing chevron on its right.Select Item Analysis.In the Select Test drop down list, select a test. ... Click Run.More items...
When the discrimination index is negative it means that the examinees in the low performing group got the answer correct at a higher rate than the higher performing group.
Item discrimination refers to the ability of an item to differentiate among students on the basis of how well they know the material being tested. Various hand calculation procedures have traditionally been used to compare item responses to total test scores using high and low scoring groups of students.
Determine the Discrimination Index by subtracting the number of students in the lower group who got the item correct from the number of students in the upper group who got the item correct. Then, divide by the number of students in each group (in this case, there are five in each group).
Item analyses are intended to assess and improve the reliability of your tests. If test reliability is low, test validity will necessarily also be low. This is the ultimate reason you do item analyses—to improve the validity of a test by improving its reliability.
Interpreting Test ResultsAlso referred to as the p-value.Ranges from 0% to 100%, or more typically written as a proportion 0.00 to 1.00.The higher the value, the easier the item.P-values above 0.90 indicate very easy items that you should not use in subsequent tests. ... P-values below 0.20 indicate very difficult items.
Quantitative item analysis happens after the items have been administered and scored. The student responses and item scores provide numeric data that is reviewed for clues about the quality of educational information produced by each item.Jun 8, 2019
The interpretation of High-Low Discrimination is similar to the interpretation of correlational indices: positive values indicate good discrimination, values near zero indicate that there is little discrimination, and negative discrimination indicates that the item is easier for low-scoring participants.
Count the total number of students answering each item correctly. For each item, divide the number answering correctly by the total number of students. This gives you the proportion of students who answered each item correctly. This figure is called the item's difficulty level.Jan 30, 2019
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.