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A die is thrown three times. A 'success' is getting a 1 or a 6 on a throw. Find the mean and variance of the number of successes.
- mu = 1, sigma² = 2/3
- mu = 2/3, sigma² = 1
- mu = 2, sigma² = 2/3
- None of these
Correct answer: mu = 1, sigma² = 2/3
Solution
With n = 3 and p = 1/3, mean = 3*(1/3) = 1 and variance = 3*(1/3)*(2/3) = 2/3.
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