Select all of the responses which are correct
Which of the following is/are true about bias and
confounding?
a. By using a placebo control and a double-blind study design, a
randomized clinical trial is immune to the possibility of bias and
confounding.
b. In a prospective cohort study, investigators find that the
hazard ratio for cardiovascular disease associated with consuming a
healthy Mediterranean dietary pattern is 0.36, 95% CI 0.21 to 0.48,
p < 0.001. Such a strong association could not be due to
residual confounding.
c. Selection bias is the likely explanation for voter exit poll
results suggesting that John Kerry had defeated George W. Bush in
the election for US President that was ultimately won by George W.
Bush.
d. Randomization is useful in clinical trials because it ensures
random distribution between the treatment conditions of known and
unknown confounders at baseline.
