109. Severalstudies have shown that hospitals are not all equally successful: patients aremuch more likely to die in some of them than in others. Since the hospitals inthe studies had approximately equal per-patient funding, differences in thequality of care provided by hospital staff are probably responsible for thedifferences in mortality rates.
Which one of thefollowing, if true, casts the most doubt on the conclusion drawn above? A. The staff in some of thehospital studies had earned more advanced degrees, on average, than the staffin the other hospitals. B. Patient populations varysubstantially in average severity of illness from hospital to hospital. C. The average number of yearsthat staff members stay on at a given job varies considerably from one hospitalto another. D. Approximately the same surgicalprocedures were performed in each of the hospitals covered in the studies. E. Mortality rates for hospital patientsdo not vary considerably from one region of the country to another.