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← JEE Main 2014 · 11 Apr · Shift 1
MathematicsSingle correct+4 / -1Question 87 of 90

JEE Main 2014 · 11 Apr · Shift 1, Mathematics question 87

If X has a binomial distribution, B(n,p)B(n,p) with parameters nn and pp such that P(X=2)=P(X=3)P(X=2)=P(X=3), then E(X)E(X), the mean of variable X, is :

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Answer and worked solution

Official answer: B

(n2)p2qn−2=(n3)p3qn−3\binom n2p^2q^{n-2}=\binom n3p^3q^{n-3} gives 3q=(n−2)p3q=(n-2)p. Then np=3q+2p=3−pnp=3q+2p=3-p.

Topics:Binomial distribution
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