Figure 10.8: Standardized scoring of Wechsler IQ tests The scoring system for Wechsler IQ tests is based on the assumption that intelligence is distributed in the population according to a normal distribution (represented by the bell-shaped curve). Thus, raw scores on the test are converted into IQ scores in such a way as to produce a normal distribution. Notice that with this system about 68 percent of IQ scores are between 85 and 115 and about 95 percent are between 70 and 130.