Volunteers are randomly assigned to a placebo or an experimental vaccine. Of the 100 who received the placebo, 2 develop a fever. Of the 100 assigned to the vaccine, 4 develop a fever. A vaccine...

Volunteers are randomly assigned to a placebo or an experimental vaccine. Of the 100 who received the placebo, 2 develop a fever. Of the 100 assigned to the vaccine, 4 develop a fever. A vaccine skeptic points out that the rate of developing a fever was twice as high in the vaccine group. Could this result be due to chance or is there reason to question the safety of the vaccine?