A large geographical area in the rural town of Mandeville in Jamaica tended to have great outbreaks of gastrointestinal illnesses among its population during the hurricane season. Researchers wanted to find out if the number of cases of illnesses had anything to do with where the inhabitants collected their drinking water. Many rural inhabitants used the river sources for their water supply throughout the area. Researchers decided to have a group of the population collect water only from the top or head of the river, another group only from the middle, and a third group only from the bottom of the river. They then assessed the number of cases of illness that resulted from each section. Which of the following statements is FALSE or DOES NOT RELATE to this research?