Stats

Question 1

In a randomised controlled trial of a new influenza vaccine, 100 patients were
randomly allocated to receive the vaccine and 100 to receive placebo. During
follow up, 20 patients who had received the vaccine contracted influenza,
compared with 30 patients who had received placebo.
Which effect did the vaccine have on the relative risk of contracting influenza?

Answer 1

RR = (20/100)/(30/100) = 0.67, which implies a 33% reduction in risk