If Surgical Procedure a Has a Higher Success Rate Than

Multiple Choice

If surgical procedure A has a higher success rate than surgical procedure B in every hospital where they are used and yet procedure B has a higher overall success rate, then we suspect that

A) Statement I: this is nonsense and it can't possibly be true.
B) Statement II: this is an example of Simpson's paradox.
C) Statement III: it must be easier to achieve success at some hospitals than at others, whatever procedure is used.
D) Statement IV: procedure B must be used predominantly in hospitals where it is easier to achieve success, while procedure A must be used predominantly where it is harder to achieve success.
E) Statments II, III, and IV are true.