1. ## Discriminating Power

There are 54 students in my class. Each student answers 10 questions. Each questions carries at most 10. Total mark is 100.

First, I want to know if discriminating power is related to the difficulty index and discrimination index. Here is what I could understand:

1/ the total score of the whole class needs to be sorted in descending.

2/ Divide 54 students into 3 groups. Focus on top 27% (15) and bottom 27% (15).

my problems are:

1/ the scores of students are not 1 or 0. Each score is between 0 and 10. So we are not calculating # correct as in the example online. Must I add a value with only 1 or 0?? and is there suggestion on how to define this value??

2/ Do I need to use Point Biserial correlation each Q and total score?? and use the p-value of the outcome?? I am still not sure if I can get the discriminating power from this.

3/ Is the correlation coefficient between each Q and the total mark useful??

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