A discrete random variable X has P(X = 1) = 0.2, P(X = 2) = 0.5, P(X = 3) = k. What is the value of k?

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Question

A discrete random variable X has P(X = 1) = 0.2, P(X = 2) = 0.5, P(X = 3) = k. What is the value of k?

Accepted Answer

0.3 — The sum of all probabilities must equal 1. Therefore k = 1 − 0.2 − 0.5 = 0.3. Option A incorrectly sets k equal to P(X = 1), perhaps assuming symmetry. Option C repeats P(X = 2), showing no calculation was performed. Option D adds rather than subtracts: 0.2 + 0.5 = 0.7, confusing the sum of known probabilities with the missing one.

Answer

0.3

Answer

0.2

Answer

0.5

Answer

0.7

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