Question: A certain rare form of cancer occurs in 37 children in a million, so its probability is 0.000037. In the city of Normalville there are 74,090,000 children. A Poisson distribution will be used to approximate the probability that the number of cases of the disease in Normalville children is more than 2. Find the mean of the appropriate Poisson distribution (the mean number of cases in groups of 74,090,000 children).
I solved this by using the Poisson distribution which is
,u = np
,u = 74,090,000 x .000037
I get 2741.33. The answer in the book is 2740. Does it matter the difference?
Probably in the book another method is used, but result is correct. I don't think accuracy matters here.