A survey is often an investigation performed in retrospect, when, for example, a tool or technique, has been in use for a while […]. The primary means of gathering qualitative or quantitative data are interviews or questionnaires. These are done through taking a sample from the population we want to investigate. The results from the survey are then analysed to derive descriptive and explanatory conclusions. They are then generalized to the population from which the sample was taken.

Wohlin, C., Runeson, P., Höst, M., Ohlsson, M., Regnell, B., & Wesslén, A. (2000). Introduction to Experimentation in Software Engineering. [-]