Lewis M. Terman (1877–1956) at Stanford University revised and refined the Binet-Simon test to increase its sensitivity at the higher end of the scale. The Stanford-Binet test, published in 1916, was the first test to use IQ scores. An IQ score (or intelligence quotient) is derived from a large sample of test results. Terman set the mean IQ score at 100 and the standard deviation at 10. By translating raw scores into IQ scores, the percentile rank of each score could be calculated. For example, an IQ score of 100 falls in the 50th percentile, of 80 in the 2.5th percentile, and one of 130 in the 99th percentile. The Stanford-Binet was the primary IQ test used for many decades and is currently in its fifth edition. In 1958, two years after Terman died, David Wechsler published the Wechsler Adult Intelligence Test (WAIS), which is now the more widely used IQ test.