CheggBooks specializes in selling and renting used textbooks. It buys its books with its online “sell books” feature, which allows college students to enter information about their books’ condition and receive cash offers. Then students ship their books to CheggBooks for payment. CheggBooks sells the used textbooks to other students via a secured credit card transaction on its website. The used books are then sent by United Parcel Service to the students who order them. The company has conducted a survey of used book buying by college students each year for the past four years. In each survey, 1,000 randomly selected college students have been asked to indicate whether they bought a used textbook in the previous year. The results are as follows:
What are the sample size implications of these data?