Question: Coronary bypass surgery, one of the most frequent in-hospital operations, consists of taking a vein or artery from somewhere in the body and using it to reroute blood around a clogged artery in the heart. However. choosing a particular surgeon to perform this operation may mean the difference between life and death, according to studies conducted in New England and Philadelphia hospitals (Mass. Medical Society Journal Watch. 8:5: New York Times. August 14, 1991, A11, also August 20. 1991. C31.

Assuming a valid random sample, test at a = .05 whether differences in the number of deaths can be attributed to chance fluctuation, or, indeed, to actual differences among the four surgeons.