GradeHub for Blackboard - Item analysisLast Updated: March 06, 2019
Item analysis in Blackboard
GradeHub provides a summary (i.e., Item Matrix) and a detailed Item Analysis to analyze your test questions.
- Select the course and exam you want to view reports for
- Select the Item Matrix tab for a summary or the Item Analysis tab for a deeper look into your exam questions.
- Both reports analyze an exam by Answer Key. If you have more than one test key, use the answer key dropdown to review results for a specific key.
- Item Matrix
- The Item Matrix is a convenient way to see the quality and difficulty of your exam.
- The bar charts display the five highest and lowest performing questions on your exam.
- Exam questions must have a point-biserial correlation >0.3 to be classified as "Highest performing questions."
- Lowest performing questions have a point-biserial correlation <0.3
- The Item Matrix detailed chart shows item discrimination using point-biserial correlation (vertical axis) and item difficulty analysis (horizontal axis) of the test questions.
- The item discrimination uses point-biserial correlation to check how well the test questions serve to discriminate between students with higher and lower levels of knowledge. In other words, it checks whether test questions are valid
- The item difficulty analysis expresses the percentage of students who answered each test question correctly. Item difficulty ranges from 0.0 (no students answered correctly; the question may have been too difficult) to 1.0 (all students answered correctly; the question may have been too easy)
This item analysis contains response frequencies with the correct answers in bold.
If a significant number of students got the question wrong, the response is shaded red.
To analyze an item's quality, the table includes the point-biserial correlation (rpb), Cronbach's alpha with delete, and upper / lower 27% for each item.
Items with a low point-biserial correlation are highlighted.
- Items where removing a given question causes test reliability of the overall (i.e., Cronbach's alpha) exam to go up (i.e., Cronbach's alpha with delete) are in red text