Item-Test Correlation

The item-test correlation is the Pearson correlation coefficient calculated for pairs of scores where one item of each pair is an item score and the other item is the total test score. The greater the value of the coefficient, the stronger is the correlation between the item and the total test. Test developers strive to select items for a test that have a high correlation with the total score to ensure that the test is internally consistent. Because the item-test correlation is often used to support the contention that the item is a “good” contributor to what the test measures, it has sometimes been called an index of item validity. That term applies only to a type of evidence called internal structure validity, which is ...