Quiz 5, Module Bias
5. What effect (if any) would you expect if the interviewers were aware of the disease status of the study subjects?
- It would benefit the validity of the results since the interviewers would understand more precisely how the exposure is related to the disease and collect better data for the cases.
- The results would likely not change.
- It could damage the validity of the results by introducing interviewer bias.
Answer (a) —
incorrect:
One of the principles of conducting a case-control study is to keep those collecting the data blinded to study subject's case status. At the same time, study participants are not told about the specific hypotheses that are being investigated in the study. If the interviewers were aware of the case-control status of participants and decided to collect more complete exposure information from the cases, but not the controls, this would result in misclassification (information bias). While sometimes it is not possible to blind interviewers to a subject's case status, continued training of interviewers and insistence on adherence to interviewing protocols would ensure that the information is collected as similarly as possible from cases and controls.
Answer (b) —
incorrect:
If interviewers were aware of the subject's disease status, they could introduce misclassification (information bias) by potentially conducting interviews differently with cases and controls.
Answer (c) —
correct:
If the interviewer is aware of disease status, this might introduce misclassification (information bias), which is characterized by more vigilant data collection (inappropriate probing, leading the subject to "correct" answers, etc.) in the case interviews than in the control interviews.
