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If XX is a Poisson variate such that P(X=3)=2P(X=4)P(X=3)=2P(X=4), then P(X=2)P(X=2) equals:

[given e−2=0.14e^{-2}=0.14]

Solution

✅ Correct Option: 4

For a Poisson variate, e−λλ33!=2⋅e−λλ44!\dfrac{e^{-\lambda}\lambda^3}{3!} = 2\cdot\dfrac{e^{-\lambda}\lambda^4}{4!}.

This reduces to 16=λ12\dfrac{1}{6} = \dfrac{\lambda}{12}, so λ=2\lambda = 2.

Then P(X=2)=e−2⋅42=2e−2=2(0.14)=0.28P(X=2) = \dfrac{e^{-2}\cdot 4}{2} = 2e^{-2} = 2(0.14) = 0.28.

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