Data collection strategy: General description and uni-mode designs

There are various ways to approach respondents for a questionnaire-based survey: respondents can complete a questionnaire with the help from an interviewer, but they can also do it themselves. Interviewers can be involved in two ways: face-to-face or via the telephone. There are also two ways for respondents to complete the questionnaire themselves: on paper, or online. This paper describes the applications, advantages and disadvantages of all these possibilities.