Case-control study

An observational controlled research study in which scientists compare two groups of people, one with a disease or condition and the other without it. The scientists then analyze the two groups to look for clues that would explain the difference (diet, lifestyle, or medical history, for instance). If one group has heart disease and the other does not, for example, the researchers might ask about behaviors such as drinking coffee. If the people with heart disease are more likely to drink coffee, this suggests that coffee may have something to do with heart disease. Because the people in the two groups might differ in many other ways, however, you need to be cautious in interpreting the results. The hypothetical study we just described shows that coffee drinking is associated with heart disease, but it does not prove that coffee drinking causes heart disease.