The New England Journal of Medicine reported on a trial of niacin in addition to a stat in drug for people with heart problems. The "end point" was a combination of deaths, heart attacks, strokes, and similar problems. The investigators said that a total of 3414 patients were randomly assigned to receive niacin (1718) or placebo (1696). They also said that the end point was reached in 16.4% of the patients receiving niacin and in 16.2% of the patients receiving the placebo.
a. How many of the patients receiving the placebo reached the end point?
b. How many of the patients receiving the niacin reached the end point?
c. In the samples, did adding the niacin result in a slightly larger or a slightly smaller percentage of people reaching the end point?
d. Is this likely to have been a controlled experiment or an observational study?