EPI short answer

Question 1.

An epidemiologic study was conducted among workers at a new pesticide manufacturing plant in

Michigan. The purpose of the study was to see if routine exposure to pesticide residue increased the risk of acute respiratory infection (ARI). All 500 workers in the plant participated in the study during a full year of follow-up and all were free from ARI at the start of the study.

Pesticide levels were monitored daily in two sections of the plant, one in which pesticides were

stored and handled on a high-volume basis and one in which non-pesticide operations took place.

425 plant workers were assigned to the high-volume pesticide location and the remaining workers

were assigned to the non-pesticide location. All workers underwent monthly health exams in which they were tested for ARI. At the conclusion of the study, 85 participants had been diagnosed with at least one ARI. 68 of these were among the workers assigned to the high-volume pesticide location and 17 among the remaining workers.

a) In two sentences, is this an example of a prospective cohort study or a retrospective cohort study? How do you know?

e) Do you believe that selection bias played a role in these study findings? Explain why or why not. 1-3 sentences.

Question 2. (20 points, 10 points each)

a. Describe an example of a retrospective cohort study. Make sure to denote the exposure and outcome and how information is collected. (3-5 sentences)

b. Using the example from 2a. Explain at least one source of bias for this study and a challenge you perceive in conducting this study. (3-5 sentences)