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Let X be the number of heads in two fair coin tosses. The variance of X is
A0.5
B1
C2
D0.25
Answer & Solution
Correct answer: A. 0.5
X is 0, 1, 2 with probabilities 1/4, 1/2, 1/4 and mean 1, so variance is 1/4 + 0 + 1/4 = 0.5.
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