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Suppose the number of accidents per week on a certain highway follows Poisson distribution with mean 2 then the percentage of weeks having no accidents is .................... (Given \(e^{-2}\) = 0.1353)

  • A.27.06%
  • B.6.77%
  • C.13.53%
  • D.7.39%

Answer: C

The percentage of weeks with no accidents is 13.53%.

For a Poisson distribution with mean m:

\[ \begin{aligned} P(X = x) &= \frac{e^{-m} m^{x}}{x!} \\ P(X = 0) &= e^{-2} = 0.1353 \end{aligned} \]

So 13.53% of weeks are expected to be accident-free.

27.06% is \(2e^{-2}\), the probability of exactly one (or exactly two) accidents, not of none. 6.77% is half of the correct figure, and 7.39% is \(e^{2}\) misread as a percentage.

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