Which form specifically assesses stability of a measure across time?

• A. Inter-rater reliability
• B. Internal consistency
• C. Test-retest reliability
• D. Content validity

Answer: (C)

Temporal stability of a measure over time is assessed by examining how consistent scores are when the same people take the test on separate occasions. This is captured by test-retest reliability: you administer the measure at two points and look at the correlation between the two sets of scores. A high correlation indicates the instrument yields similar results across time, suggesting it is measuring a stable trait rather than something that fluctuates or is heavily affected by measurement error. Considerations include choosing an appropriate time interval; if it’s too short, memory or practice effects can inflate stability, and if it’s too long, real changes in the construct can deflate it. Inter-rater reliability concerns agreement between different raters and does not address time stability. Internal consistency looks at how well the items relate to each other within a single administration, not across time. Content validity concerns whether the instrument covers the intended domain, not how scores hold up over time. Therefore, the form that specifically assesses stability across time is test-retest reliability.