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Question 270014
JEE Mathematics · Hard

Probability: JEE Advanced MCQ

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JEE AdvancedHardQuestion 270014

Question

If X is a binomial random variable B(n, p) with mean 6 and variance 2, then n equals:
  1. A
    9
    Correct
  2. B
    18
  3. C
    6
  4. D
    12

Correct answer

9

Explanation

Mean = np = 6, Variance = np(1−p) = 2. So np(1−p)/(np) = 2/6 → 1−p = 1/3 → p = 2/3. Then n = 6/p = 6/(2/3) = 9.

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