Standard Scale
The standard scale is a statistical analysis of a subject’s score. It is derived from a normal frequency curve or bell-shaped curve. The Mean, which is the arithmetic average, and Standard Deviation (S.D.) numbers are provided in PPM as well as in the New Instruction Charts, which are labeled as Figure 2 (A-H) on pages 9-16. Generally, 68 percent of scores fall between –2 and +2 S.D.’ 99.70 percent between –3 and +3 S.D. There are a very small percentage of scores that fall either above or below 3 S.D. from the Mean. The instructions for scoring appear in the Using New Interpretation Charts section of page 7.