Aim and content This is a generic course. This means that the course is reserved for PhD students at the Graduate School of Health and Medical Sciences at UCPH. Anyone can apply for the course, but if you are not a PhD student at the Graduate School, you will be placed on the waiting list until enrollment deadline. After the enrolment deadline, available seats will be allocated to the waiting list. The course is free of charge for PhD students at Danish universities (except Copenhagen Business School). Special rules apply for research year students enrolled at Faculty of Health and Medical Sciences at UCPH. All other participants must pay the course fee. Learning objectives A student who has met the objectives of the course will be able to: a. Know the basic principles for questionnaire development and validation. b. Develop, validate, apply, and analyze a simple questionnaire. c. Evaluate the quality of a questionnaire presented in a medical article. Content 1. The early stages of questionnaire development: Problem formulation, identification of key concepts, conceptualisation, variable definition. 2. Questionnaire development: Principles for item development. 3. Multi-item scales: Rationale, construction, and basic principles. 4. Testing and validation of questionnaires: Pre-testing and cognitive interviewing techniques. Principles and methods related to content, construct, and criterion validity and reliability. 5. Development of questionnaires vs. use of standardized questionnaires: advantages and disadvantages and how to combine approaches. 6. Overview of psychometric methods based on classical test theory and modern psychometric methods (differential item functioning, item response models). 7. Conducting a good questionnaire study: practical aspects, data collection, and strategy. 8. Analysing the data, dealing with missing data, reporting results.