Matched pairs or independent/separate samples For each of the prompts below, decide whether the parameter of interest is a paired difference in means (matched pairs, μd ), or a difference in means (independent samples, μ1−μ2 ). 1. Students want to know if it matters where they have their cell phone screen repaired. A sample of eight cell phones with broken screens was obtained. For each phone, an estimate for the screen repair in U.S. dollars (\$) was obtained from a local store and from an online merchant. Your goal is to determine if, on average, the estimate in dollars for the total repair from the on-line merchant is more (possibly because of the added cost of shipping) than the estimate from a local store. Identify the unit/case: parameter of interest: 2. A study wants to determine how free Wi-Fi affects data usage on a long-distance bus ride. A group of nine buses traveling from State College to New York City were randomly assigned to give free Wi-Fi to passengers and another nine buses traveling the same route were randomly assigned to offer Wi-Fi for a one-time charge for its passengers. The study measured the amount of data used, in gigabytes, on each bus for one trip to find out the difference in the average amount of data used based on if Wi−Fi is free or a paid service. Identify the unit/case: parameter of interest: 3. An advertising firm seeks to compare two advertisements for the same product, so pairs of its product users are matched based on age, sex, and income. A coin is flipped to assign the two advertisements to the two product users in each pair. The advertising firm compares average users' willingness to purchase the product for the two advertisements. Identify the unit/case: parameter of interest:
