Questionnaires have several advantages? (2)
3.Questionnaires are annoymous & don't require respondent to sit face-to-face with an interviewer makes them suitable for sensitive topics e.g. national survey of sexual attitudes and lifestyle was a postal questionnaire rather than face-to-face structured interview
4.large sample can given a questionnaire, if the sample is representative the questionnaires should produce representative data so it can be used to make generalisations