One of your authors lives in an urban area and sometimes relies on ride-sharing apps to get around. Her year-end report from Uber included two data points based on her own history with the app. The following questions quote from the report, but also suggest hypothetical studies that might use these data. For each question, state the variables, identify what type of variable each is, indicate which is the independent variable and which is the dependent variable, and note the appropriate statistical test. Explain why you suggested that test.

a. “You joined 1777 days ago.” Do early adopters of Uber use the ride-sharing service more often than newer users do? More specifically, does the number of days since you’ve joined Uber predict how many times a month you use the service?

b. Based on a rider rating of 4.9, Uber wrote, “Thanks for being such a great passenger,” which, admittedly, the company likely says to everyone. Do those who typically ride during the day have higher ratings than those who typically ride at night?