Two Tests with the Same Mean and Different Standard Deviations

These two graphs of the scores on a test show that it is difficult to interpret the meaning of an individual's score on a norm-referenced test without knowing the standard deviation of the scores, that is, without knowing how variable the scores are. For example, in a group with a mean of 78, a 90 would be a fairly average score or a very high score, depending on the variability of the scores. (Source: Woolfolk, Educational Psychology, 6E, 1995 by Allyn & Bacon. All rights reserved.) (Link to Study Help #3)