Certified Rehabilitation Counselor Practice

Which of the following describes a measure of internal consistency calculated between items?

1. Criterion validity

2. Parallel forms reliability

3. Cronbach's alpha

4. Test retest reliability

The correct answer is: Cronbach's alpha

Cronbach's alpha is a widely used statistic that measures the internal consistency of a set of items, typically within a survey or questionnaire. Internal consistency refers to the extent to which all items in a measurement scale assess the same construct or concept. It provides a way to understand how closely related the items are as a group. When items have high internal consistency, it suggests that they are measuring the same underlying concept and thus can be considered as reliable indicators of that construct. Cronbach's alpha is calculated based on the average inter-item correlation among the items; values range from 0 to 1, with higher values indicating greater reliability. In contrast, criterion validity involves assessing how well one measure predicts an outcome based on another measure, which does not pertain to internal item consistency. Parallel forms reliability refers to the consistency of scores across different forms of the test but does not measure the relationships among items within the same form. Test-retest reliability measures the stability of test scores over time, focusing on the temporal aspect rather than the internal consistency among items.