Control variables are the variables (i.e., factors, elements) that researchers seek to keep constant when conducting research. In a typical research design, a researcher measures the effect an independent variable has on a dependent variable. To properly measure the relationship between a dependent variable and an independent variable, other variables, known as extraneous or confounding variables, must be controlled (i.e., neutralized, eliminated, standardized).

Although control variables are not the central interest of a researcher, they are paramount to properly understand the relationship between independent and dependent variables. If extraneous variables are not controlled in a research project, they can skew the results of a study. If used properly, control variables can help the researcher accurately test the value of an independent variable on ...