poisson distrubutiins
distributions that arise when counting random events with key properties
processes and events of poisson
for histograms described by Poisson distributions
mew = sigma squared
poisson approximation to binomial
can be made if n is large and p is small enough and np<10
- when n is large and p is small, then X~B(n,p)
mew = np, sigma squared = np(1-p) = np = mew
X~Pois(n,p)
if X has a Poisson distribution with mean mew and written X~poiss(mew)
then p(k) = (e^-mew mew^k)/k! k is an integer