Normal approximation
If n is large, and p is not too
close to 0 or 1, the binomial distribution can be approximated by a normal
distribution. Practically, the Normal approximation can be used when
both np ≥10 and n(1 − p) ≥10.
If X
is the count of successes in the sample, the sampling distribution for
large sample size n is:
approximately N (µ = np, σ = Önp(1
− p))