In a very long manuscript 80 of the pages contain no typogra

In a very long manuscript, 80% of the pages contain no typographical errors. Assuming that the number of errors per page is a random variable with a Poisson distribution, what percentage of the pages have two or more typographical errors?

Solution

Possion Distribution
PMF of P.D is = f ( k ) = e- x / x!
Where   
= parameter of the distribution.
x = is the number of independent trials

P( X < 2) = P(X=1) + P(X=0)   
= e^-0.8 * 2 ^ 1 / 1! + e^-0.8 * ^ 0 / 0!   
= 0.8088
P( X > = 2 ) = 1 - P (X < 2) = 0.1912 ~ 19.12% of the pages have two or more typographical errors