A researcher wants to find out the average number of books the region of Waterloo residents purchased in the year 2020. A random sample of 5 households was chosen from the residential address list of the Waterloo region. The number of books purchased last year by each resident in the selected households is recorded. The total number of books purchased last year and the total number of residents of the sampled households are listed in the following table. Didatpdf (a) Name the sampling design and give a mason why this sampling design is used in this study. [2 rrtarks} (b) What are the sampling units and the observation units in this study? [2 marks] (c) Based on the sample data, estimate the average number of books the region of Waterloo residents purchased in the year 2020 and consthct a 95% confidence interval. There are about 210,000 households in the region of Waterloo. and the average household size is 2.5. [T marks] Household # books residents OT ID CO NO H OT CHAN 10 6 Total 30 15