In the June 2007 issue, consumer reports examined top laoding and front loading washing machines, testing samples of several differant brands of each type. 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 (mtop-mfront) 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 (mTop - mFront = 0)what's the corresponding alpha level?