If one variable is hypothesized to cause or influence another one, social scientists call the first variable the independent variable. The second is termed the dependent variable because it is believed to be influenced by the independent variable. A representative sample is a selection from a larger population that is statistically typical of that population. The most frequently used representative sample is a random sample in which every member of the entire population has the same chance of being selected. The scientific method requires that research results be both valid and reliable.
Validity refers to the degree to which a measure or scale truly reflects the phenomenon under study.
Reliability refers to the extent to which a measure provides consistent results. A survey is a study, generally in the form of an interview or questionnaire, that provides sociologists with information concerning how people think and act. Among the United States' best-known surveys of opinion are the Gallup poll and the Harris poll. Surveys can be indispensable sources of information, but only if the sampling is done properly and the questions are worded correctly. This method allows sociologists to examine certain behaviors and communities that could not be investigated through other research techniques.