Which term was originally defined as the ratio of mental age to chronological age multiplied by 100?

• A. Mental age
• B. IQ
• C. Stanford-Binet
• D. Intelligence quotient (IQ)

Answer: (D)

The idea being tested is how the intelligence score was originally defined. The intelligence quotient, or IQ, was so named because it was calculated as a ratio: mental age divided by chronological age, then multiplied by 100. This means a person whose mental abilities match their actual age would score 100; higher mental-age relative to actual age yields above-100 scores, and lower yields below-100. This ratio-based definition was the origin of the term IQ, and it frames what the score represents—how a person’s cognitive development compares to typical age norms. The other terms point to related ideas (mental age itself, the test holding the name Stanford-Binet, or the abbreviation for the concept) but they do not describe the original ratio formula that gave birth to the term intelligent quotient. Today IQ is often reported as deviation scores, but the historical definition is all about that mental-age-to-chronological-age ratio multiplied by 100.