Part 1: Here is a fictionalized report similar to what you might read as part of a newspaper article, borrowing ideas from a real study.

Results of a recently released study show that high doses of antioxidant vitamins don't reduce the risk of diabetes in women at high risk of heart disease. Researchers had been hopeful, since other research suggests that oxidative stress is a key factor impairing the body's ability to secrete insulin.

The researchers recruited 8000 female health professionals with either a history of or at least two risk factors for heart disease. Participants were given either a supplement including large daily doses of vitamin E (600IU), vitamin C (500mg) and beta carotene (70,000 IU), or a placebo. After nine years there were no statistically significant differences in the rate of diabetes between the groups.

1. Is this a retrospective, prospective, or randomized experimental design study? How do you know?

2. This study sets out to test a particular hypothesis, but the evidence fails to support it. What is the hypothesis (i.e., what is C, what is E, and is C hypothesized to be a positive or negative causal factor for E)?