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