Methodological Urban Legends: The Misuse of Statistical Control Variables

The automatic or blind inclusion of control variables in multiple regression and other analyses, intended to purify observed relationships among variables of interest, is widespread and can be considered an example of practice based on a methodological urban legend. Inclusion of such variables in most cases implicitly assumes that the control variables are somehow either contaminating the measurement of the variables of interest or affecting the underlying constructs, thus distorting observed relationships among them. There are, however, a number of alternative mechanisms that would produce the same statistical results, thus throwing into question whether inclusion of control variables has led to more or less…