According to a recent FCC survey, one in six cell phone users have experienced "bill shock" from unexpectedly high cell phone bills (Tech Daily Dose, May 26, 2010).

a. Discuss the sampling distribution of the sample proportion based on a sample of 200 cell phone users. Is it appropriate to use the normal distribution approximation for the sample proportion?

b. What is the probability that more than 20% of cell phone users in the sample have experienced "bill shock"? L056