Elementary Statistics: Picturing the World (6th Edition)

If np $\geq$ 5 and nq $\geq$ 5 we can use the normal distribution to approximate the binomial. np = 15 $\times$ 0.70 = 10.5 nq = 15 $\times$ 0.30 = 4.5 Since np $\geq$ 5 and nq $\lt$ 5, we cannot use the normal distribution to approximate the binomial.