Dogsled drivers, known as mushers, use several different breeds of dogs to pull their sleds. One proponent of Siberian Huskies believes that sleds pulled by Siberian Huskies are faster than sleds pulled by other breeds. He times 4747 teams of Siberian Huskies on a particular short course, and they have a mean time of 5.45.4 minutes. The mean time on the same course for 4545 teams of other breeds of sled dogs is 6.66.6 minutes. Assume that the times on this course have a population standard deviation of 1.31.3 minutes for teams of Siberian Huskies and 1.91.9 minutes for teams of other breeds of sled dogs. Let Population 1 be sleds pulled by Siberian Huskies and let Population 2 be sleds pulled by other breeds.   Step 1 of 2 :   Construct a 99%99% confidence interval for the true difference between the mean times on this course for teams of Siberian Huskies and teams of other breeds of sled dogs. Round the endpoints of the interval to one decimal place, if necessary.

In 2016, the Honors College at a large state university claimed that the average GPA of its graduating students is 3.80. Later that year, a new service-learning requirement was added to the graduation requirements, despite student claims that this additional requirement would take away from the time devoted to their studies and likely lower their GPAs. Last month, the dean of the Honors College randomly selected 10 graduating students and recorded their GPAs. His recorded data is as follows:   3.85 3.95 4.00 3.61 3.83 3.73 3.69 3.81 3.73 3.78   Using the appropriate six-step non-parametric testing procedure, is there sufficient evidence at the α = 0.05 significance level to conclude that average GPA of graduating students has decreased since the service-learning requirement was added?

A woman who has moved into a new house is trying to determine which of two routes to work has the shorter average driving time. Times in minutes for six trips on route A and five trips on route B are as follows: A: 16.0 15.7 16.4 15.9 16.2 16.3 B: 17.2 16.9 16.1 19.8 16.7 Can you conclude that the mean time is less for route A?

Many freeways have service (or logo) signs that give information on attractions, camping, lodging, food, and gas services prior to off-ramps. These signs typically do not provide information on distances. An article reported that in one investigation, six sites along interstate highways where service signs are posted were selected. For each site, crash data was obtained for a three-year period before distance information was added to the service signs and for a one-year period afterward. The number of crashes per year before and after the sign changes were as follows. Before: 14 29 62 123 64 62 After: 15 27 41 84 76 71 (a) The article included the statement "A paired t test was performed to determine whether there was any change in the mean number of crashes before and after the addition of distance information on the signs." Carry out such a test. [Note: The relevant normal probability plot shows a substantial linear pattern.] State and test the appropriate hypotheses. (Use a = 0.05.)…