A survey of randomly selected university students found that 93 of the 105 first-year students and 97 of the 135 secondyear students surveyed had purchased used textbooks in the past year. (a) Construct an 80% confidence interval for the difference in the proportions of firstyear and secondyear university students who purchased used textbooks. (Round your answers to 4 decimal places, if needed.) Answer: ( . ) (b) If a 90% confidence interval for the difference in proportion of first-year and second-year university students who purchased used textbooks is (0.0856, 0.2488). Give an interpretation of this confidence interval. ' We are 90% confident that the first-year students at this university bought between 8.56% and 24.88% more used textbooks than second-year students. We know that 90% of all random samples done on the population will show that the proportion of first-year students who bought used textbooks is between 8.56% and 24.88% higher than the proportion of second-year students who bought used textbooks. \\ We know that 90% of the first-year students bought between 8.56% and 24.88% higher than the proportion of second-year students who bought used textbooks. \\ We are 90% confident that, at this university, the proportion of first-year students who bought used textbooks is between 8.56% and 24.88% higher than the proportion of secondyear students who bought used textbooks. We are 90% confident that, at this university, the proportion of second-year students who bought used textbooks is between 8.56% and 24.88% higher than the proportion of firstyear students who bought used textbooks. r'll'll