Questionnaires are a commonly used technique for collecting primary data in which respondents answer the same set of questions. They can be used for explanatory or descriptive research or as part of a mixed methods design. The validity and reliability of questionnaire data depends on careful design including question wording and type, pre-testing, and choosing an appropriate administration method like email, mail, phone or in-person. Design elements like layout, question order and response format also impact the quality of data collected.