The exclusive use of actual (raw) performance data to measure salesmen's contributions to the firm can be misleading. It should be limited to comparisons of selling under similar circumstances and when a .single performance measure is used. To make dissimilar data more comparable, the authors suggest using the Standard Deviation, a statistical estimate of the amount of variation or dispersion of a group of measures from the average (mean). Its use in the technique of the Z score or standard score can place different measures of performance on the same measuring scale. The authors gives the formula and examples of assessing both intragroup and intergroup performance. © 1969.