3.19 Does aspirin cure headaches? A study enrolled 100 college students who had frequent headaches to participate in a study to examine the effects of aspirin on their headaches. The students were instructed to take aspirin when they had a headache and to report whether there was a substantial relief from the headache pain within an hour.
(a) Explain why this study is biased.
(b) How would you change the study to remove the bias? Explain your answer.