NDA 2025 · PYQ · Probability / Binomial distribution · easy
Let X be a random variable following binomial distribution whose mean and variance are 200 and 160 respectively. What is the value of the number of trials (n)?
A.500
B.1000✓ Correct
C.1500
D.2000
Explanation
For binomial distribution: mean = np = 200, variance = npq = 160. Dividing: q = 160/200 = 4/5, so p = 1/5. Then n = 200/p = 200/(1/5) = 1000.
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