1. For a university study estimating a population proportion, the researcher wants to work at a 70% confidence level, what would be the critical value, Za/2 , used for this confidence interval? [2] 2. In the year 2015 Youth Risk Behavior survey done by the U.S. Centers for Disease Control, 64% of 650 female 12th graders said they always use a seatbelt when driving. [4] a) Construct a 99% confidence interval for the proportion of 12th grade females in the population who always use a seatbelt when driving. b) If 1300 students were surveyed instead of 650, how would this affect the width of the confidence interval? (don't need to calculate the exact interval, just describe how it would change) c) If you were asked to construct an 80% confidence interval as opposed to 99%, how would this affect the width of the confidence interval? (don't need to calculate the exact interval, just describe how it would change)