Question

The number of typing errors made by a typist has a Poisson distribution with an average of five errors per page. If more than five errors appear on a given page, the typist must retype the whole page. What is the probability that a randomly selected page does not need to be retyped

Answer 1

0.61596

Explanation:

Given that:

λ = 5 (5 errors per page)

Poisson distribution formula :

P(x = x) = (λ^x * e^-λ) / x!

Probability that page does not need to be retyped means that error on page is less than or equal to 5

P(x ≤ 5) = p(x = 5) + p(x = 4) +... + p(x = 0)

The individual probabilities can be obtained using the formula above or the use of a calculator

P(x ≤ 5) = 0.17547 + 0.17547 + 0.14037 + 0.08422 + 0.03369 + 0.00674

P(x ≤ 5) = 0.61596