3. Recognize the difference between a reliability coefficient and standard error of measurement. A reliability coefficient is the correlation between the scores of test takers on two independent replications of the measurement process. Reliability refers to the degree to which test scores are free from measurement error for a given group of test takers. The SEM uses reliability information to indicate the amount of error associated with the estimate of an individual’s true score. Therefore, the SEM estimates how much a test-taker’s observed score might vary over repeated administrations of the test.