Akindi uses the point-biserial correlation coefficient (rpb) to calculate a discriminatory score for each question in your assessment, as well as for the assessment as a whole.
The discriminatory score shows the relationship between students correctly answering each question and their overall performance on the assessment. It reflects how well each question distinguishes between high-performing and low-performing students.
Here’s what the scores mean:
Score above 0.20: These questions are well-designed. High-performing students tend to answer them correctly, and low-performing students tend to get them wrong. If your questions fall into this category, they’re probably doing a good job of assessing your students.
Score between 0.00 and 0.20: These questions may need improvement. Both high and low-performing students answer them correctly about the same amount. Consider rewording these questions to make them clearer or remove any confusion.
Score below 0.00: These questions are problematic. High-performing students are getting them wrong, and low-performing students are getting them right. Check these questions carefully to make sure the wording is clear or that the answer key is correct. Akindi will even tell you which incorrect answers were most commonly chosen.
The overall discriminatory score for the assessment is the average of the individual question scores, excluding any questions with a weight of 0.
When calculating the discriminatory score, question weights are not taken into account, except for zero-weighted questions, which are excluded from the overall assessment score.
