What is discrimination in blackboard?

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.

What does discrimination mean on test questions?

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.

What is the difference between difficulty and discrimination index?

Index of Difficulty: This is the percentage of the total group which has responded incorrectly to the item (including omissions). Index of Discrimination:This is the difference between the percent of correct responses in the upper group and the percent of correct responses in the lower group.

What does a high discrimination index mean?

A discrimination index of 0.3 or greater is considered highly discriminating. Note: Item discrimination indicates the extent to which success on an item corresponds to success on the whole test. Any item with negative or zero discrimination will affect the discrimination of an assessment​.

How would you determine the discrimination level of a test item?

For each item, subtract the number of students in the lower group who answered correctly from the number of students in the upper group who answered correctly. Divide the result by the number of students in one group. The Discrimination Index is listed in decimal format and ranges between -1 and 1.

Blackboard Learn Quick Hit Video - Item Analysis

What does a discrimination index of 0.34 mean in the test item analysis?

Discrimination index (DI) value of less than 0.2, more than 0.34 and between 0.2-0.34 are considered as poor, excellent, and acceptable discriminating questions, respectively. The DE will be zero % if all the distractors were NFDs and DE will be 100% of all the distractors were functional.

What is the difference between 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 is a good discrimination score?

Lower discrimination scores (in red) are scored +0.24 or lower; good scores (green) are +0.25 or higher.

What does a discrimination index of below 0.20 mean?

The discrimination index ranges from 0–1; closer to 1 indicates a higher discrimination value. If it is less than 0.2, it is a poor discrimination item; 0.2–0.29 is a fair item, 0.3–0.39 is a good item, and over 0.4 is a very good item with a high degree of discrimination [13].

What is the acceptable item difficulty range?

Item Difficulty Index

It can range between 0.0 and 1.0, with a higher value indicating that a greater proportion of examinees responded to the item correctly, and it was thus an easier item. For criterion-referenced tests (CRTs), with their emphasis on mastery-testing, many items on an exam form will have p-values of .

What should a teacher do with a test item that has negative discrimination index?

This means that the test should be unidimensional. Items with negative discrimination indices must be deleted or replaced. Classroom teachers must rewrite all items with zero discrimination indices.

What does a negatively discriminating item do on a classroom test?

Items with a negative discrimination are theoretically indicating that either the students who performed poorly on the test overall got the question correct or that students with high overall test performance did not get the item correct. Thus, the index could signal a number of problems.

How does difficulty index and discrimination index help you as a teacher?

Difficulty index (P) and Discrimination index (D) are two parameters which help evaluate the standard of MCQ questions used in an examination, with abnormal values indicating poor quality.

What is the definition of discrimination for students?

Discrimination is unfair treatment of one particular person or group of people. Usually the different treatment is because of the person's sex, religion, nationality, ethnicity (culture), race, or other personal traits.

What is zero discrimination index?

If an item has a discrimination index of 0, it indicates it is not discriminating at all – i.e. the same number of people in the higher group got it correct as in the lower group.

How do you solve for difficulty index?

It is calculated using the formula P=R/T, where P is the item difficulty index, R is the number of correct responses and T is the total number of responses (which includes both correct and incorrect responses).

What does an item falling at the range of 0.20 0.29 discrimination index mean?

Discrimination Indices within each Discriminascion range. (Discrimination Range 0.20 to 0.29: "Marginal items, usually needing, and being subject to, improvement. ")

What does a discrimination value of more than 0.40 mean?

11, 12 Discrimination index of 0.40 and up is considered as very good items, 0.30–0.39 is reasonably good, 0.20–0.29 is marginal items (i.e. subject to improvement), and 0.19 or less is poor items (i.e. to be rejected or improved by revision).

How do you calculate discrimination index for essay questions?

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).

What is a negatively discriminating item?

When the discrimination index is negative it indicates that the item may have low validity; this occurs if the examinees in the low performing group got the answer correct at a higher rate than the higher performing group.

What is positive item discrimination?

A positive item discrimination means a higher proportion of people in the top group chose the answer than in the bottom group. A high positive value for the correct answer generally means the question is a good discriminator, which is what we want (but is difficult to achieve!).

What is an example of item difficulty?

Definition: The item difficulty uses the percentage of students who got a particular question correct as a measurement of question difficulty. For example: If 85% of students got the question correct, then it is considered a low-difficulty item.

How do you calculate item difficulty and item discrimination?

Calculating Item Difficulty

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.

What does a negative discrimination index mean?

If the discrimination index is negative, that means that for some reason students who scored low on the test were more likely to get the answer correct. This is a strange situation which suggests poor validity for an item.