Cronbach Alpha with Deletion

Cronbach Alpha with Deletion

Cronbach Alpha with Deletion helps assess test question reliability.

How? It asks whether the exam as a whole is more reliable if you simply delete the question under review. Basically, the Cronbach Alpha with Deletion re-runs the exam's KR(20) without the question under review. If the exam as a whole is more reliable without it, there's probably something wrong with that question.

The Cronbach Alpha with Deletion generally ranges between 0.0 and +1.0, but it can fall below 0.0 with smaller sample sizes.

More important than its range is how the Cronbach Alpha with Deletion compares to the exam's KR(20). If a question's Cronbach Alpha with Deletion is greater than the exam's KR(20), it means the exam as a whole is more reliable without it. For example, take a look at Question No. 2 in the picture below. If the exam's KR(20) is 0.545, then we know Question No. 2 is "suspect" because its Cronbach Alpha with Deletion of 0.686 is greater than 0.545.

EAC suggestion: Look out for questions with a Cronbach Alpha with Deletion greater than the exam's KR(20). These questions, which EAC Visual Data highlights in red, decrease overall test reliability and should be considered suspect.

See other test statistics: