From this data they can attempt to prove that either eating Ajax can cause colon cancer or that colon cancer victims have a proclivity to eating Ajax. They make a determination and then release it to peer review. Other epidemiologists will try to reproduce the study to prove or disprove the findings. Often they will find that the study was not accurate after discovering that they could find a group of 100 people who have eaten Ajax with no incidence of colon cancer. This will go on and on for years before anything conclusive is learned.
Epidemiology is a very complex science.
The media picks up these studies and runs with them as stories, even though the studies are in various stages of their completion. The media is very irresponsible while reporting these claims, as they will often act as if these studies actually proved something, when usually they have just raised enough questions to warrant further investigation into the matter. Which brings me back to doctors. Gone are the days where doctors would work only 3 days a week and golf every afternoon. With the prevalence of HMOs and Medicare patients, doctors are finding themselves in a position of working longer hours and having to take more patients.