In the past year Harborville has had an unusually high rate of new cases of a certain disease. An investigation revealed that over the past five years Harborville' s public water supply has had a high level of pollutants. Medical researchers have hypothesized that Harborville' s water is responsible for the high rate of new cases of the disease.
Some of the people with newly diagnosed cases of the disease began to develop the disease before Harborville's water became polluted does not provide additional support for the researchers' hypothesis.