Suppose that you are a researcher, and you're interested in the possible effects of calcium on joint health. You conduct a study that measures joint health and calcium levels in a random sample of 675 people who died in good health. You find that 8.5% of the 82 people with low calcium levels had poor joint health when they died. However, only 1% of the 593 people with regular calcium levels had poor joint health.
Which of the following statistical designs best describes measuring joint health and calcium levels in a random sample from 675 people?
Group of answer choices
a. Experiment
b. Randomized comparison
c. Observational study