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Continuing the IRS audit example with X ~ P(2), what is P(x≥3), the probability that at least three of the 100 taxpayers are audited?
A0.1353
B0.6767
C0.3233
D0.1804
Answer & Solution
Correct answer: C. 0.3233
1. P(x≥3) is the complement of P(x≤2), so P(x≥3) = 1 - P(x≤2).
2. Summing the Poisson pmf for x = 0, 1, and 2 with μ = 2 gives P(x≤2) ≈ 0.6767.
3. So P(x≥3) = 1 - 0.6767 ≈ 0.3233.
4. Option B is P(x≤2) itself, the complement of the value asked for, not the answer.
_Source: OpenStax Introductory Statistics (CC BY 4.0), Ch 4 "Discrete Random Variables", section 4.6 Poisson Distribution_
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