Question

9. A secretary makes 2 errors per page on the average. What is the probability that on the next page she makes;
   1. 4 or more errors?
10. 2. No errors?

Answer 1

This is a question of poisson distribution with
Mean () = 2
For a Poisson Distribution

a) P(X 4) = 1 - P(X < 4)
P(X 4) = 1 - P(X = 0) - P(X = 1) - P(X = 2) P(X = 3)

b)
P(X = 0) = 0.1353352832366127
P(X = 0) = 0.1353
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