this question comes from the verbal review 2nd edition. page 139 #55
Q: There is a great deal of geographical variation in the frequency of many surgical procedure- up to tenfold variation per hundred thousand people between different areas in the numbers of hysterectomies, prostatectomies, and tonsillectomies.
To support a conclusion that much of the variation is due to unnecessary surgical procedure, it would be most important to establish which of the following?
Answer: (B) The variation is unrelated to factors (other than the surgical procedures themselves) that influence the incidence of diseases for which surgery might be considered.
The GMAT's reasoning for the answer is that, "unless the possibility of such geographical variations in the incidence of pertinent medical conditions is ruled out, it would be risky to conclude that the variation is attributable to unnecessary surgical procedure."
Can someone please tell me what this all means!!! I cant figure the logic behind the answer or reasoning. Thank you.