CAIE FP2 2012 June — Question 8

Exam BoardCAIE
ModuleFP2 (Further Pure Mathematics 2)
Year2012
SessionJune
TopicExponential Distribution
TypeLink Poisson to exponential

8 The number of flaws in a randomly chosen 100 metre length of ribbon is modelled by a Poisson distribution with mean 1.6. The random variable \(X\) metres is the distance between two successive flaws. Show that the distribution function of \(X\) is given by $$\mathrm { F } ( x ) = \begin{cases} 1 - \mathrm { e } ^ { - 0.016 x } & x \geqslant 0
0 & x < 0 \end{cases}$$ and deduce that \(X\) has a negative exponential distribution, stating its mean. Find
  1. the median distance between two successive flaws,
  2. the probability that there is a distance of at least 50 metres between two successive flaws.
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