alleryFor a random variable X, the variance Var(X) equals
AE(X)²
B[E(X)]² − E(X²)
CE(X²) − [E(X)]²
DE(X) − E(X²)
Answer & Solution
Correct answer: C. E(X²) − [E(X)]²
1. Variance measures the spread of X around its mean.
2. By definition Var(X) = E[(X − μ)²].
3. Expanding: Var(X) = E(X²) − 2μE(X) + μ² = E(X²) − μ² = E(X²) − [E(X)]².
4. This is the standard computational form for variance.
_Source: syllabus Mathematics, Ch 13 "Probability", §13.6_
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