Which tool is commonly used in public health research?

Surveys and questionnaires are commonly used tools in public health research due to their ability to gather a large amount of data efficiently from diverse populations. They can be designed to collect information on a variety of health-related behaviors, beliefs, attitudes, and demographic characteristics. By using structured questions, researchers can quantify responses, making it easier to analyze trends and correlations related to public health issues.

These tools allow for both qualitative and quantitative data collection, enabling researchers to capture nuanced information while also delivering statistically significant results. Additionally, surveys can be distributed in various formats (online, face-to-face, by mail), thus maximizing reach and accessibility, which are essential in public health research.

The other options, while they may have their applications in specific contexts, are not as universally applicable in public health research. Focus groups are useful for in-depth qualitative insights but don't allow for large-scale quantitative analysis. Experimental trials in laboratories are critical for biomedical research but not primarily for public health epidemiology. Case studies provide detailed information about specific instances but lack the broader applicability and generalizability that surveys and questionnaires offer.