The control group and experimental group are compared against each other in an experiment. The only difference between the two groups is that the independent variable is changed in the experimental group. The independent variable is "controlled" or held constant in the control group.
The questionnaires are a cheap and quick and the effective way to obtain large amounts of information form a large sample of people. As they are open and closed type they give the respondent enough time to think and respond and are beneficial for the quantitative and the qualitative data.
