Questionnaires are a research tool used to collect data from individuals in a standardized and structured way. They typically consist of a set of questions that are designed to elicit specific information from respondents. Questionnaires can be administered in various ways, including online, through mail, in person, or over the phone.

Questionnaires can be used for a wide range of research purposes, including surveys of public opinion, market research, psychological research, and medical research. They can also be used in the context of social science research to collect data on a variety of topics, including attitudes, beliefs, behaviors, and demographics.

The design of a questionnaire is important to ensure that the questions are clear, unambiguous, and relevant to the research question being addressed. Researchers also need to consider issues such as response bias, sample selection, and data analysis when designing a questionnaire.