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A random variable X has the distribution X = 1,2,3,4 with P(X) = 0.1, 0.2, 0.3, 0.4 respectively. Its mean and standard deviation are respectively:
- 3 and 2
- 3 and 1
- 3 and sqrt(3)
- 2 and 1
Correct answer: 3 and 1
Solution
E(X) = 3 and E(X²) = 10, so variance = 10 - 9 = 1 and the standard deviation is 1.
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