THE FEUTEX TOOLKIT

Exam Item Group Discrimination

Compare a question’s correct-response rates in two equal-sized score groups.

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01 Your input

Group sizestudents/groupUpper correctstudentsLower correctstudents

02 Your result

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Result data

Formula

Upper rate = 100*upper_correct/group_size; Lower rate = 100*lower_correct/group_size; Discrimination = (upper_correct-lower_correct)/group_size; Combined difficulty = 100*(upper_correct+lower_correct)/(2*group_size)

How to use this tool

Enter the measured quantities and your own planning assumptions.
Review all calculated outputs and the stated limitations.

Try this example

{
  "group_size": 20,
  "upper_correct": 17,
  "lower_correct": 8
}

Accuracy and scope

Descriptive upper-minus-lower index for equal groups. Does not establish test validity, statistical significance or a recommended cutoff.

Is my data uploaded?

This tool runs locally in your browser. Input and output are not sent to a processing server. Copy or download your result before leaving the page.