Part 6: Match the sources of bias with the type of study design and the best way to minimize the bias. Type of study design: a. Case-Control b. Cohort Way to minimize bias a. Obtain controls from the same work environment as cases b. Obtain controls from the general population. c. Incentives d. Take steps to assure that mild, clinically resolved or fatal cases are represented in the case group e. Refer to medical records containing exposure information if they exist 1. Loss to follow-up 2. Recall, interviewer 3. Healthy worker effect 4. Berkson's bias 5. Nevman's bias Study Design Way to minimize bias