Question ID:PT5 S3 Q2 Passage:Several studies have shown that hospitals are not all equally successful: patients are much more likely to die in some of them than in others. Since the hospitals in the studies had approximately equal per-patient funding, differences in the quality of care provided by hospital staff are probably responsible for the differences in mortality rates. Stem:Which one of the following, if true, casts the most doubt on the conclusion drawn above? Correct Answer Choice:BChoice A:The staff in some of the hospitals studied had earned more advanced degrees, on average, than the staff in the other hospitals. Choice B:Patient populations vary substantially in average severity of illness from hospital to hospital. Choice C:The average number of years that staff members stay on at a given job varies considerably from one hospital to another. Choice D:Approximately the same surgical procedures were performed in each of the hospitals covered in the studies. Choice E:Mortality rates for hospital patients do not vary considerably from one region of the country to another.