•For <N> greater than about 10, p(N) is practically indistinguishable
from
g(N) = Exp(-(N-<N>)2/(2N))/Sqrt(2pN)
which
is the Gaussian distribution with mean <N> and
standard
deviation Sqrt(<N>)
•It is a very useful rule-of-thumb that in any measurement that can be traced to a
counting
process, the uncertainty in the count is the square root of the count