There’s another type of deviation that you may read about, and you should know what it means. The mean deviation (also called the mean absolute deviation) is the sum of the absolute value of the deviations from the mean divided by the number of scores. You already know that the sum of the deviations from the mean must equal zero (otherwise, the mean is computed incorrectly). That’s why we square the deviations before summing them. Another option, though, would be to take the absolute value of each deviation (which is the value regardless of the
