Investigators Conducting a Study Regarding the Effects of Water Pollution

Essay

Investigators conducting a study regarding the effects of water pollution and peptic ulcer disease obtained the following data:
A population of 9000 men and women, aged 45, were examined on January 1, 1985. Of these people, 6000 were exposed to toxins in the local water supply and 3000 were not. At the time of this exam, 90 cases of peptic ulcer disease were discovered; 60 of these cases were among those exposed to toxins in their local water.
All the people at the initial exam who were free from peptic ulcer disease were followed with repeat exams over the following year. This study revealed 268 new cases in the total group; of these, 238 cases were among those exposed to toxins in their local water.
A. Calculate the prevalence per 1000 people of peptic ulcer disease on January 1, 1986:
Among the exposed
Among the nonexposed
B. Calculate the 1985 incidence rate/1000 people of peptic ulcer disease:
Among the exposed
Among the nonexposed