An inspector inspects shipments of medications to determine

An inspector inspects shipments of medications to determine the efficacy in terms of the proportion that failed to retain full potency 60 days after production. This proportion is thought to be 0.048. How many pills must be inspected in order to use a normal approximation?

Solution

By convention and generally agreed conditions,

minimum sample size (n) should be 30.

So at least 30 pills should be inspected. More than 30 is always preferred.