8.7 Station Statistic Analysis
The Station Statistic Analysis shows the performance on questions in written exams.
Item | Description | Useful links |
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33% Discrimination | Item discrimination is the degree to which students with high overall exam scores also got a particular item correct. The Station Statistic analysis uses 33% cohort to calculate the discrimination by:
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Discrimination (point-biserial) | The item discrimination index is a point biserial correlation coefficient. Its possible range is -1.00 to 1.00. A positive result indicates that there is a high correlation between higher performing candidates giving a correct response to the item. | |
Facility (difficulty) of correct answer | Facility is a measure of how easy or difficult is a question for candidates. It is calculated as: |
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Frequency | Frequency of answers |
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Quintile Graph | For SBA type items it works like this: all candidates sorted by score (from the highest to the lowest) are split to 5 groups and then the graph shows % of candidates who got the question correctly in each group. The graph should usually shows "steps down" because most of top scored candidates should get the question right. Not the same for CPQ Graph. |
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