Reference no: EM132464434

A study published in the British Medical Journal compared two treatments for kidney stones:

Treatment A: Open surgical procedure.

Treatment B: A procedure with only small puncture wound.

Each of the 700 patients who participated in this study were classified according to which treatment he/she received (A or B), and the outcome (Success, Failure). 

The results of the study show that overall, Treatment B was more effective. However, it was also discovered that when the 700 patients are separated into those who had large stones and those who had small stones, within each of the two groups separately, Treatment A is more effective. 

Which of the following statement is incorrect?

A. The results of the study are mathematically impossible. If Treatment B is more effective overall, then it must also be more effective within each of the two groups separately.

B. The stone size (small large) is a lurking variable in this example.

C. This is an example of Simpson's Paradox.

D. In this study Treatment (A or B) is the explanatory variable and Outcome (Success, Failure) is the response variable.