A manufacturer claims that its new hand sanitizer reduces the number of days an average person is sick in a year. To test this claim, a researcher decided to conduct an experiment. The researcher randomly selected 300 people, divided into subject groups by age. Over the course of a year, all the subjects regularly used the hand sanitizer. At the end of the year, the researcher compared the number of days that the subjects in each group were sick. Which statements about this experiment are true?