A questionnaire is an instrument used to collect data through a set of questions printed on a form. There are several steps to designing an effective questionnaire, including planning what to measure, formatting the questions, sequencing questions, and pretesting the questionnaire. Pretesting involves testing the questionnaire on a small sample to identify any issues and ensure the questions will obtain the desired information. Key aspects of designing good questions involve using clear wording, an appropriate scale of responses, and considering the flow and order of questions.