One advantage of using a questionnaire is that it is easy to quantify the results using closed questions or content analysis. The use of closed questions enables the researcher to collect quantitative data, as well as the open questions still giving the opportunity to collect in depth qualitative data. This is an advantage as it enables trends and comparisons and helps reaserachers understand what is the result of the IV or the first co-variable.
One advantage of using questionnaires is that they are easily replicable, resulting in them being a standardised procedure. This is an advantage as all participants (mention context of scenario here when in exam) are receiving the same questions in the same order improving the reliability of the research.