Which of the following studies would be considered an example of statistical inference?

a. A study involving a large number of heart bypass patients found that the patients who took vitamin E supplements for several weeks before the operation had significantly better heart function after the procedure than the patients who took placebo (sham) supplements.

b. Before this season's Super Bowl, a newspaper prints a bar graph displaying the distribution of past Super Bowl Most Valuable Players by position.

c. A news magazine tabulates the number of auto accidents, number of related injuries, and number of related fatalities in each year from 1995 to 2005.