Statistical survey is a method used to collect in a systematic way, information from a sample of individuals. Although most people are familiar with public opinion surveys that are reported in the press, most surveys are not public opinion polls (such as political polling), but are used for scientific purposes. Surveys provide important information for all kinds of research fields, e.g., marketing research, psychology, health professionals and sociology. A survey may focus on different topics such as preferences (e.g., for a presidential candidate), behavior (smoking and drinking behavior), or factual information (e.g., income), depending on its purpose. Since survey research is always based on a sample of the population, the success of the research is dependent on the representativeness of the population of concern (see also sampling (statistics) and survey sampling).