For each study described below, comment on the extent to which inferences can be drawn about a larger population and whether cause and effect can be established.

Part A A basketball coach thinks lessons in dance will improve the agility of his players and thereby reduce injuries. To test his theory, he hosts an optional weekly dance practice for any of his players that wish you participate. At the end of the season, he compares agility for those athletes who participated in dance training and those who did not. (8 points) Part B A student wishes to determine if staying up all night "cramming" for an exam improves performance. She explores this question by asking everyone in her Calculus class to write down on a piece of paper his or her score on a recent test and total number of hours of sleep he or she got on the last three nights before taking the test. (8 points) Part C Does Lysine, a popular over-the-counter cold sore remedy that claims to reduce the length and severity of cold sores really work? A consumer advocacy group addresses this question by asking a random sample of 250 adults how many cold sores they'd had in the last six months, how long each cold sore lasted, and if they took Lysine to treat the cold. (8 points)