What type of reliability is expected when a measure assesses a stable trait over time?

The correct answer is based on the understanding of how reliability in psychological measurement works, particularly the concept of test-retest reliability. This type of reliability is specifically designed to assess the stability of a measure when it is administered at different points in time. When a test or measure is expected to evaluate a trait that does not change significantly over time, such as intelligence or personality traits, it is essential to ensure that the results remain consistent upon repeated administrations.

In test-retest reliability, researchers administer the same test to the same group of individuals at two different time points and then correlate the scores from both times. A high correlation suggests that the measure consistently captures the stable trait over that period, thus confirming that the measure is reliable when evaluating enduring characteristics.

In contrast, internal reliability evaluates the consistency of results across items within a single test. Interrater reliability assesses the degree of agreement between different raters or observers, and parallel forms reliability examines the consistency of two different test forms measuring the same construct. These other types are relevant in their own contexts, but they do not specifically address the stability of traits over time like test-retest reliability does.