### LON-CAPA Help

The Overall Problem Statistics page lets you view performance statistics on all problems. This page displays the following data about the Folders/Sequences selected for evaluation:

• #Items

The number of assessment items (problem parts) in the sequence.

• Score and Count Statistics

For the score, the product of the problem weight, the percent awarded, the count, and the number of problem parts correct, the following data are computed:

• MEAN

• Standard Deviation

• Maximum

The highest achieved score or count in the data set.

• Minimum

The lowest achieved score or count in the data set.

• N

The number of students evaluated.

• KR-21

This statistic measures the internal reliability of the data set. This statistic is relevant for exams only. Let K be the number of items in your test, M the mean score on the test, s the standard deviation of the scores on your test, then the KR-21 statistic, rk, is given by the formula

 rk= K K-1 · 1-(M*(K-M)) Ks2

You have the option to have this statistical data output to an Excel file.

Clicking on the problem name will open a view of the problem in a separate window.