16.31 Ride-sharing data around the world and choosing the right statistical test: 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 a number of data points, many of which involved how Uber is used around the world. The following questions quote from the report but also suggest hypothetical studies that might use these data. For each question, state the types of variables, 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. New York is known as the city that never sleeps, but Uber thinks Chicago, known as the Windy City, may have stolen that title: “The Windy City is also the city that never sleeps. It had the most rides between 2 am and 6 am. Maybe the wind keeps them up?” Do cities with frequently changing weather have more Uber riders in the wee hours of the night? Imagine you could categorize cities as either having changeable weather or nonchangeable weather.

b. Which countries use Uber the most? The top three in Uber’s global rankings are the United States, Brazil, and India. Uber reports that “riders in these countries really went the distance this year, traveling more miles than anyone else.” Is having a higher gross domestic product (in terms of U.S. dollars) related to more Uber rides in a country? (Trick question! See Category 4 on the decision tree.)

c. Uber has an offshoot app called Uber Eats. Yes, you can order an Uber for your food! The company tracked the most popular orders, including “the world’s most popular sugar fix, ” doughnuts. Uber apparently delivered so many of the circular treats that it can legitimately report that “people ordered enough to fill the Eiffel Tower four times.” Suppose you wondered whether foodordering behavior varied between those who live in North America versus Europe. More specifically, does the ratio of orders of burritos, pizza, and doughnuts vary between North America and Europe?

d. Which is the most forgetful city in the world? According to Uber, it’s New York City. “The Big Apple has a short memory when it comes to their belongings. We would give them a medal, but they’d probably forget it in an Uber trip.” New York City attracts a lot of tourists as well as a lot of day visitors from the surrounding areas in upstate New York and Long Island, New Jersey, and Connecticut. And, of course, there are locals. Do these three groups—tourists, day-trippers, and locals—differ in the number of belongings they have ever left behind in an Uber car in New York City? (We acknowledge that the mean number of belongings for each group will be a small number because most will leave nothing.)