Question: Suppose as part of your job you are responsible for installing emergency lighting in a series of state office buildings. Bids have been received from four manufacturers of battery-operated emergency lights. The costs are about equal, so the decision will be based on the length of time the lights last before failing. A sample of four lights from each manufacturer has been tested, with the following values (time in hours) recorded for each manufacturer:

Type A       Type B       Type C      Type D

1,024         1,270         1,121          923

1,121         1,325         1,201          983

1,250         1,426         1,190         1,087

1,022         1,322         1,122         1,121

Using α = 0.01, what conclusion for the four manufacturers should you reach about the median length of time the lights last before failing? Explain.