Certified in Public Health (CPH) Practice Exam

What is the primary purpose of double-blinded (masked) studies?

1. To ensure comparability between cases and controls.

2. To reduce observer and interviewee bias.

3. To eliminate the risk of sampling variation.

4. To enhance the sample size for the study.

The correct answer is: To reduce observer and interviewee bias.

The primary purpose of double-blinded (masked) studies is to reduce observer and interviewee bias. In a double-blind study, neither the participants nor the researchers know which individuals are receiving the treatment and which are in the control group. This design is crucial for maintaining the integrity of the data collected during the study. By preventing both parties from having knowledge of group assignments, the study minimizes the potential for biases that could influence the results. For example, if a researcher knows which participants are receiving treatment, their observations or reporting may be unconsciously affected by that knowledge. Similarly, participants may alter their responses based on their beliefs about the treatment they are receiving. Thus, the double-blind approach is essential for ensuring that the findings of the study are attributable to the treatment itself rather than external influences or biases from either party. The other options do not encompass the primary goal of the double-blinded study design. While ensuring comparability between cases and controls, eliminating sampling variation, and enhancing sample size can be important aspects of study design, they are not the main focus of implementing a double-blind methodology.