alleryThe variance of the number of heads in 3 fair-coin tosses is
A3/4
B1/4
C1
D3/2
Answer & Solution
Correct answer: A. 3/4
1. n = 3, p = 1/2, q = 1 − p = 1/2.
2. For Binomial, variance = n × p × q.
3. = 3 × 1/2 × 1/2 = 3/4.
4. Standard deviation is √(3/4) = √3 / 2.
_Source: syllabus Mathematics, Ch 13 "Probability", §13.6_
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