Normal Approximation to the Binomial
If:
n · p ≥ 5
n · (1 − p) ≥ 5.
The binomial distribution B(n, p) can be approximated by the normal distribution:
Example
In a particular city, one in three families have a phone in their home. If 90 families are chosen at random, calculate the probability that at least 30 of them will have a phone.
