A questionnaire is a research tool consisting of a series of questions designed to gather information from respondents. It can be used in various fields, such as psychology, market research, and sociology, to collect data on opinions, behaviors, or demographics. Questionnaires can be administered in different formats, including paper, online, or face-to-face. Typically, questionnaires include multiple-choice questions, open-ended questions, or rating scales. They are valuable for collecting quantitative and qualitative data, allowing researchers to analyze trends and patterns. Properly designed questionnaires can lead to reliable and valid results, making them essential in many studies and surveys.