Survey (human research)
Survey research is often used to assess thoughts, opinions, and feelings. Surveys can be specific and limited, or they can have more global, widespread goals. Psychologists and sociologists often use surveys to analyze behavior, while it is also used to meet the more pragmatic needs of the media, such as, in evaluating political candidates, public health officials, professional organizations, and advertising and marketing directors. A survey consists of a predetermined set of questions that is given to a sample. With a representative sample, that is, one that is representative of the larger population of interest, one can describe the attitudes of the population from which the sample was drawn. Further, one can compare the attitudes of different populations as well as look for changes in attitudes over time. A good sample selection is key as it allows one to generalize the findings from the sample to the population, which is the whole purpose of survey research.
Observational techniques
In marketing and the social sciences, observational research (or field research) is a social research technique that involves the direct observation of phenomena in their natural setting. This differentiates it from experimental research in which a quasi-artificial environment is created to control for spurious factors, and where at least one of the variables is manipulated as part of the experiment. 
Observational research is a method of data collection that has become associated with qualitative research. Compared with quantitative research and experimental research, observational research tends to be less reliable but often more valid. The main advantage of observational research is flexibility. The researchers can change their approach as needed. Observational research measures behavior directly, rather than the subject's self-reports of behavior or intentions. The main disadvantage is it is limited to behavioral variables. It cannot be used to study cognitive or affective variables.