The Item Reliability report in Gradient provides statistical values for both the assignment and each item within the assignment.
From within an assignment report, go to the Assignment Summary section to find the Item Reliability report. Read on to learn more about the information displayed in this report.
Cronbach Alpha / KR20 (Item Reliability)
Cronbach's Alpha was developed by Lee Cronbach in 1951, with the intent of determining if multiple-choice tests or surveys were reliable. The value is normally between 0 and 1, where the closer the value is to 1, the more reliable the test is considered to be. Reliability refers to how well a test is at actually gauging a student's knowledge of the material. A number of factors may be worth considering when looking into a test that has either a high or low value:
- If the value is on the higher end, that could point to too many questions on the test that are asking the same thing.
- If the value is on the lower end, it's possible that there are not enough questions, and/or the questions on the test are not as closely related to each other as they could be.
A value between -1 and 1 that measures individual question reliability. The closer the value is to 1 the more reliable the question is. This value is determined by correlating the student's score on that question with how they did on the entire test. For a question with a high Point Biserial value, students that struggled on the test as a whole generally struggled on that question. The reverse is true as well - students who did very well on the test as a whole generally did well on that question.
Cronbach Alpha with Item Deletion (Cronbach Del)
This is the Cronbach Alpha value for the assignment as if the question being looked at had been removed. If the value is higher than the overall test Cronbach Alpha value, then removing the item would most likely improve the test's reliability. These items are marked in red on the list.
Average: The average percent score of all scans for the assignment.
Scans: The total number of scans for the assignment.
Std. Dev: The Standard Deviation of the student scores for the assignment.
Cronbach Alpha/KR20: The Cronbach Alpha value, as described above.
Possible Score: Possible points for the assignment.
Maximum Score: The highest score achieved by a student for the assignment.
Minimum Score: The lowest score achieved by a student for the assignment.
Score Range: The difference between the highest score achieved by a student, and the lowest score achieved by a student for the assignment.
Median Score: The median (or middle) student score for the assignment.
Mean Score: The average of all student scores for the assignment.