What does a high standard error of measurement indicate?

A high standard error of measurement indicates a high likelihood of true scores falling outside the observed scores. This concept arises from the understanding that any measurement, including psychological assessments or academic tests, will have some degree of error. The standard error of measurement quantifies that error, suggesting that if an individual were to take the same test multiple times, their observed scores could fluctuate significantly due to various factors, such as test conditions or the individual's state at the time of testing.

When the standard error of measurement is high, it implies that there is considerable uncertainty about where the individual's true score lies on the underlying scale. This means that the observed score may not accurately reflect the individual's true level of ability or attribute being measured, leading to a greater chance that the actual ability will fall outside of the range indicated by the observed score. Education and psychological testing often use this metric to understand the limitations of their assessments better and to communicate the potential range of true scores to stakeholders.