CAIE S2 2024 June — Question 7

Exam BoardCAIE
ModuleS2 (Statistics 2)
Year2024
SessionJune
TopicPoisson Distribution
TypeConditional probability with Poisson

7 The independent random variables \(X\) and \(Y\) have the distributions \(\operatorname { Po } ( 1.9 )\) and \(\operatorname { Po } ( 2.2 )\) respectively.
  1. Find \(\mathrm { P } ( X + Y < 4 )\).
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  2. Find the probability that \(X = 2\) given that \(X + Y < 4\).
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  3. A sample of 60 randomly chosen pairs of values of \(X\) and \(Y\) is taken,and the value of \(X + Y\) is calculated for each pair.The sample mean of these 60 values is found. Find the probability that the sample mean of \(X + Y\) is less than 4.0 .
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