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Question: Answered & Verified by Expert
In a book of 500 pages, it is found that there are 250 typing errors. Assume that Poisson law holds for the number of errors per page. Then, the probability that a random sample of 2 pages will contain no error, is :
MathematicsProbabilityTS EAMCETTS EAMCET 2006
Options:
  • A $e^{-0.3}$
  • B $e^{-0.5}$
  • C $e^{-1}$
  • D $e^{-2}$
Solution:
2745 Upvotes Verified Answer
The correct answer is: $e^{-1}$
Here number of errors per page
$=\frac{250}{500}=\frac{1}{2}$
and $\quad n=2$
$\therefore \quad \lambda=n p=2 \times \frac{1}{2}=1$
and probability of no error
$P(X=0)=\frac{e^{-1} \times(1)^0}{0 !}=e^{-1}$

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