ABSTRACT
The test factor, it should be stressed, is introduced solely for the purpose of increasing one understands of the original two-variable relationship. At least six types of test factors may be distinguished: extraneous variables, component variables, intervening variables, antecedent variables, suppressor variables and distorter variables. A central theoretical contribution of taking account of extraneous variables is that it guards against the erroneous or misleading interpretation. A striking example of the theoretical importance of considering control variables appears in a study by Herbert Goldhamer and Andrew W. Marshall. The significant theoretical contribution was, however, questioned by Lawrence Haber. Haber noted that in the 1930s child-care advice, guided by the theory of behaviorism, stressed restriction and control, whereas in the 1940s, under the influence of Dewey and others, more permissive practices were the vogue. Daniel R. Miller and Guy E. Swanson suggested that location in the economic system would create a family integration setting which would influence the choice of child-rearing practices.
