A drill manufacturer wants to draw attention to a new design, which, theoretically, allows quicker changes between drill bits. The manufacturer gathers a random sample of 20 amateurs who have some experience using drills around the home. They are asked to complete a pre scribed set of tasks with the new drill and with the old drill (which drill is used first is randomly assigned). The total time to complete the tasks (in minutes) is recorded for each drill. The order of subtraction is (time with the new-style drill - time with the old-style drill).The average difference is -5.2, with a standard deviation of 12.2. Is there sufficient evidence to suggest that the tasks are completed more quickly with the new-style drill? Use α = 0.05.You may assume the differences in completion times are normally distributed.

  • CreatedJuly 12, 2015
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