How much do users pay for Internet service? Here are the monthly fees (in dollars) paid by a random sample of 50 users of commercial Internet service providers in August 2000:
20 40 22 22 21 21 20 10 20 20
20 13 18 50 20 18 15 8 22 25
22 10 20 22 22 21 15 23 30 12
9 20 40 22 29 19 15 20 20 20
20 15 19 21 14 22 21 35 20 22
(a) Make a plot of the data (this could be a histogram, stemplot, boxplot, or normal probability plot). Be sure to describe what the plot looks like. Are the t procedures justified? Explain.
(b) Give a 95% confidence interval for the mean monthly cost of Internet access in August 2000.