Q. 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
A) $e^{- 0.3}$
B) $e^{- 0.5}$
C) $e^{- 1}$
D) $e^{- 2}$
Explanation
(c)
Here, number of errors per page
$p = \frac{150}{500} = \frac{1}{2}$
$and\ n = 2$
$\therefore\ \lambda = np = 2 \times \frac{1}{2} = 1$
and probability of no error
$P(X = 0) = \frac{e^{- 1} \times (1)^{0}}{0!} = e^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.