Which formula is used to calculate the traditional ratio IQ?
2017
Which formula is used to calculate the traditional ratio IQ?
- A.
Mental age × Chronological age
- B.
Chronological age ÷ Mental age
- C.
(Mental age ÷ Chronological age) × 100
- D.
Chronological age + Mental age
Show answer & explanation
Correct answer: C
Concept
Traditional ratio IQ compares a person's mental age with chronological age. Because the ratio is expressed on a scale centred at 100, it is converted to that scale by multiplying by 100.
Application
Let MA denote mental age and CA denote chronological age.
Form the age ratio as MA ÷ CA.
Express the ratio on the IQ scale: IQ = (MA ÷ CA) × 100.
Therefore, the applicable expression is (Mental age ÷ Chronological age) × 100.
Cross-check
If mental age equals chronological age, then MA ÷ CA = 1 and the formula gives IQ = 100, the centre of the traditional ratio scale. Hence the formula is (Mental age ÷ Chronological age) × 100.