questionnaire

A questionnaire is a research instrument consisting of a set of questions or statements designed to collect information from respondents. They are used to obtain quantitative data, qualitative responses, or both, and are common in social sciences, market research, public health, and organizational studies. Questionnaires can be self-administered or interviewer-administered, and may be delivered on paper or online.

Questionnaires differ in format. Closed-ended questions with predefined options enable straightforward coding and statistical analysis, while open-ended items capture detail. Scales, such as Likert-type items, measure attitudes or perceptions. Good design emphasizes clear wording, neutrality, logical sequencing, and avoidance of double-barreled or biased items. Pre-testing or piloting helps identify problems before full deployment.

Validity and reliability are central. Content validity ensures coverage of the intended domain; construct validity assesses whether items reflect the underlying concept. Reliability includes consistency over time (test-retest) and internal consistency (e.g., Cronbach’s alpha). The administration mode (online, mail, telephone, in-person) affects reach and data quality, and sampling and response bias influence representativeness.

Data from questionnaires are typically coded and analyzed with descriptive statistics, cross-tabulations, or inferential models. Ethical considerations include informed consent, confidentiality, and protection of sensitive information. Advantages include cost-effectiveness, standardization, and scalability; disadvantages include nonresponse, social desirability bias, and limited depth. Questionnaires have evolved with sampling theory, measurement development, and digital collection tools.