Pub. date: 2008 | Online Pub. Date: November 27, 2007 | DOI: 10.4135/9781412953948 | Print ISBN: 9781412928168 | Online ISBN: 9781412953948| Publisher:SAGE Publications, Inc.About this encyclopedia
Stacie Ezelle Taylor
In research design, a control variable is defined as a variable that is known to or expected to influence the dependent variable and might also affect the explanatory or independent variable in an analysis, but is not the focus of interest for the researcher. The influence of a control variable may interfere with the main analysis, for instance, by obscuring between-treatment or between-group differences, or creating apparent relationships between variables of interest. Often variables of this type are used to create blocks in an experimental design or stratify a sample. Occasionally, the examination of the influence of control variables is called ‘elaboration of the analysis’ because they are not the variables of main interest in the analysis. Within the realm of designed experiments, a control variable may be kept constant or controlled for each test or replication of the experiment. In observational studies, control variables are often used in analysis ...