statistics
posted by ashley .
The average number of radioactive particles passing through a counter during 1 millisecond in a lab experiment is 4. What is the probability that more than 2 milliseconds pass between particles?

What is the variability of this count? More information needed.

I've been working this out and can't get the answer shown in the book...I use mu = 1/4 thus lambda = 4 P(X > 2) = 1(1F(x)) = e^4x = e^8 This is not the answe given however so I am lost on this one.