The average monthly cable television bill is estimated to be $99.10 (source: Yoni Heisler, “The average cable bill has increased by nearly 40% in 5 years,” http://bgr.

com, Sep. 9, 2015). Suppose the study used to arrive at this estimate had a margin of error of $1.25 and a confidence level of 95%. Suppose the standard deviation of the monthly cost of cable television bills is $10.00.

a. Determine the sample size of the study.

b. Calculate the sample size required to decrease the margin of error by a dollar.

c. A typical sample size used in national surveys is 1,500 to 2,000. Determine a range for the margin of error corresponding to this range of sample sizes.