# Homework Help: Stochastic modelling, poisson process

1. Apr 7, 2012

### staty

1. The problem statement, all variables and given/known data
Suppose a book of 600 pages contains a total of 240 typographical errors. Develop a poisson approximation for the probability that three partiular successive pages are error-free.

3. The attempt at a solution

I say that the number of errors is poissondistributed with errorate 240/600=0.4 errors/pages.

The probability of 0 errors for 3 pages is:

(3*0.4)^0*e^(-3*0.4)/0!=e^(-1.2)

But the answer index says that the answer is e^(-12). That is, there should not be a dot there, why?

2. Apr 8, 2012

### bizboy1

Looks right to me. It could be an error in the back of the book.

3. Apr 8, 2012

### Office_Shredder

Staff Emeritus
Just as a gut check, if each page had a .4 chance of an error independently, the chance of no errors would be .63 = .216. Your answer numerically is .3 which is fairly close, while the answer in the back of the book says that the odds of these three pages having no errors in on the order of one in a million, which sounds pretty unreasonable