It is difficult to establish the causal link between cigarette smoking and lung cancer because
A) random allocation of subjects to smoking is unethical.
B) observational studies generally cannot rule out confounding.
C) those who choose to smoke may be genetically at greater risk for lung cancer than those who don't choose to smoke.
D) experiments done on animals may not be valid for humans.
E) All of the above

Question

Quizplus · Accepted Answer

Each of the reasons provided (A, B, C, D) contributes to the difficulty in establishing a causal link between cigarette smoking and lung cancer, making E the correct choice. Random allocation to smoking groups is unethical (A), observational studies have issues with confounding variables (B), genetic predispositions could influence who chooses to smoke (C), and animal studies may not directly translate to human outcomes (D).

It Is Difficult to Establish the Causal Link Between Cigarette