
Question performance graph
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* Add median to the question performance graph
* Add a gray dashed horizontal line at 50% of y-axis to ease identification of problematic question
* Suggesting corrective anchor.
   Corrective anchor =  SUM(P_j * Percent_j) - SUM(P_i * Percent_i)
    - P: point of that question
    - Percent: percent of student passing that question
    - i: questions where student did not perform well, e.g., % achieved less than 50%
    - j: questions where students perform very well and is a free-lunch questions, e.g., % achieved more than 90%
   Explanation: it is the weighted difference of score that students achieved too high and too low.

Histogram of total raw score
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* Add a vertical line indicating the passing threshold

