IQ is calculated by
IQ is typically calculated using the ratio of mental age to chronological age, multiplied by 100. The classic formula is (Mental Age / Chronological Age) × 100. So the correct answer should be that option.
Now, for the core concept: IQ measures cognitive abilities relative to age. The formula adjusts for age differences, so a child with a higher mental age than their actual age would have a higher IQ.
Why the correct answer is right: The formula compares an individual's problem-solving abilities to the average for their age group. For example, a 10-year-old with a mental age of 12 would have an IQ of 120. This standardizes the score across different age groups.
Wrong options: If there were other formulas like chronological age divided by mental age, or using a different multiplier, those would be incorrect. Also, if an option suggested a fixed score without age adjustment, that's wrong. Any formula not involving the ratio would be invalid.
Clinical pearl: Remember the ratio and the multiplication by 100. Modern IQ tests might use different methods, like deviation IQ, but the traditional formula is key for exams.
Need to structure the explanation with all the required sections, keeping it concise under 2500 characters. Make sure each part is clear and accurate for medical students preparing for exams like NEET or USMLE.
**Core Concept**
IQ (Intelligence Quotient) is a standardized measure of cognitive ability calculated by comparing an individual's mental age to their chronological age. The classical formula is **(Mental Age / Chronological Age) × 100**, reflecting relative cognitive performance adjusted for developmental stage.
**Why the Correct Answer is Right**
The correct formula accounts for age-related variations in cognitive development. For example, a 12-year-old with a mental age of 15 would have an IQ of 125 [(15/12) × 100]. This ratio ensures scores are norm-referenced, comparing individuals to their age group. Modern tests (e.g., Wechsler scales) use deviation IQs (mean = 100, SD = 15), but the foundational principle remains the same.
**Why Each Wrong Option is Incorrect**
**Option A:** *"Chronological Age / Mental Age × 100"* inverts the ratio, producing a score inversely related to actual intelligence.
**Option B:** *"Mental Age × Chronological Age"* lacks normalization, making scores arbitrary and non-comparable across age groups.
**Option C:** *"Chronological Age + Mental Age"* ignores the proportional relationship critical for age-adjusted assessment.
**Clinical Pearl / High-Yield Fact**
Remember the classic formula: **(Mental Age ÷ Chronological Age) × 100**. Modern IQ testing uses statistical deviation from population norms, but exam questions often focus on the traditional ratio method. Avoid confusing "mental age" with "chronological age"—a common trap in psychometric assessments.
**Correct Answer: C. (Mental Age / Chronological Age