What does the standard error of measurement (SEM) represent?

• A. The standard deviation of the test.
• B. The average observed score.
• C. The minimal detectable change.
• D. The expected range of error around an observed score due to measurement variability.

Answer: (D)

SEM is the standard deviation of the measurement errors, reflecting how much an observed score is expected to differ from the true score because the measurement isn’t perfectly reliable. In practice, if you could administer the test many times under identical conditions, the scores would center around the true score with a spread about the SEM. A more reliable test yields a smaller SEM, meaning less expected fluctuation due to measurement. This concept is about the variability intrinsic to the measurement itself, not the overall score distribution across people, and it’s distinct from the minimal detectable change, which concerns detecting real change beyond measurement error. So the SEM represents the expected range of error around an observed score due to measurement variability.