The average of values or quantities. Known also as simple average or arithmetic average. Compute an average as the sum of all value amounts divided by the number of values tallied. For example, the mean of 1, 2, 3, 4, and 5 is (15 / 5) = 3. Mean quickly identifies the midpoint on a scale of a varied, scattered number of instances. It can be distorted if extreme values exist often. This distortion can be measured by mean deviation or standard deviation . Also refer to median and mode.