Which of the following methods is preferred for determining the reliability of an instrument?

Test-retest reliability is considered the preferred method for determining the reliability of an instrument because it measures the consistency of an instrument over time. Essentially, this method involves administering the same instrument to the same group of individuals on two different occasions. If the results are similar across both administrations, the instrument is deemed reliable. This approach provides quantitative evidence of stability and consistency, which are essential for ensuring that the instrument produces dependable results in different contexts and times.

In contrast, face validity, content validity, and construct validity assess different aspects of an instrument's effectiveness or appropriateness. Face validity looks at whether an instrument appears to measure what it is supposed to measure, but this does not truly reflect its reliability. Content validity evaluates whether the instrument covers a representative sample of the construct being studied, while construct validity examines whether the instrument accurately reflects theoretical concepts. Although these validity measures are important for ensuring the relevance and appropriateness of an instrument, they do not provide a direct measure of reliability over time like test-retest reliability does. Thus, test-retest reliability is preferred for assessing the reliability of an instrument.