6. A professor would like to investigate whether people who frequently get full dash body scans are more likely than people who do not get full dash body scans to get
brain cancer. From the students in his class, he picks half at random to get full dash body
scans each week and half to not ever get a full dash body scan. Fifty years from now, he
will analyze whether more people who frequently get full dash body scans got brain
cancer than people who do not get full dash body scans.
a. Is this an experiment or an observational study? Why?
b. Summarize at least three practical difficulties with this planned study.