Second load of wash The Consumer Reports article described in Exercise 52 continued their investigation of washing machines. One of the variables the article reported was “cycle time,” the number of...

Second load of wash The Consumer Reports article described in Exercise 52 continued their investigation of washing machines. One of the variables the article reported was “cycle time,” the number of minutes it took each machine to wash a load of clothes. Among the machines rated good to excellent, the 98% confidence interval for the difference in mean cycle time (m_Top
- m_Front) is (-40, -22).

 a) The endpoints of this confidence interval are negative numbers. What does that indicate?

 b) What does the fact that the confidence interval does not contain 0 indicate?

 c) If we use this confidence interval to test the hypothesis that m_Top
- m_Front
= 0, what’s the corresponding alpha level?

Exercise 52

Washers In the June 2007 issue, Consumer Reports also examined the relative merits of top-loading and frontloading washing machines, testing samples of several different brands of each type. Suppose the study tested the null hypothesis that top- and front-loading machines don’t differ in their mean costs, and the test had a P-value of 0.32. Would a 95% confidence interval for contain 0? Explain.