The Binet–Simon and Stanford–Binet Tradition

We need to say that one of the first usable intelligence tests was developed by Binet and Simon, while an important later idea for expressing results as an intelligence quotient was developed by Stern.

The early test is known today as the Binet–Simon Scale. It was designed for educational assessment of children and became an important foundation for later intelligence testing. FreeIQTest.info is not a Binet–Simon or Stanford–Binet test; the history is presented here for educational context.

Soon after the development of this scale, it was adapted in the United States and became known as the Stanford–Binet Intelligence Scale. The 1916 Stanford revision became highly influential in U.S. intelligence testing. A historical form of the score was calculated by dividing the test taker's mental age by chronological age and then multiplying this number by 100. For example, a child with a mental age of 12 and a chronological age of 10 would have an IQ of 120 (12 / 10 × 100).

Stanford–Binet Intelligence Scale

If mental age was the same as chronological age in this historical ratio system, the IQ would equal 100. An IQ of 100 therefore represented performance at the expected age level. Higher or lower ratios indicated performance above or below that age comparison.

Modern context: Contemporary standardized intelligence tests do not simply apply this old mental-age formula to adults. They use age-based normative samples and modern psychometric methods, so historical cutoffs should not be applied directly to today's clinical assessments.