Before discussing quantitative theories, it is important to understand variables and the types that are used in forming theories. A variable refers to a characteristic or attribute of an individual or an organization that can be measured or observed and that varies among the people or organization being studied.This variance means that scores in a given situation fall into at least two mutually exclusive categories (Thompson, 2006). Psychologists prefer to use the term construct (rather than variable), which carries the connotation more of an abstract idea than a specifically defined term. However, social scientists typically use the term. Variables often measured in studies include gender;age; socioeconomics status (SES); and attitudes or behaviors such as racism, social control, political power, or leadership. Several texts provide detailed discussion about the types of variables one can use and their scales of measurement. Variables are distinguished by two characteristics: (a) temporal order and (b) their measurement (or observation).
Temporal order means that one variable precedes another in time. Because of this time ordering, it is said one variable affects or causes another variable;though a more accurate statement would be that one variable probably causes another. When dealing with studies in the natural setting and with humans, researchers cannot absolutely prove cause and effect, and social scientists now say that there is “probable causation.” Temporal order means that quantitative researchers think about variables in an order from “left to right”(Punch, 2005) and order the variables in purpose statements,research questions, and visual models into left-to-right, cause-and-effect type presentations. Thus, see the following:
- Independent variables are those that (probably) cause, influence, or affect outcomes. They are also called treatment manipulated antecedent or predictor variables.
- Dependent variables are those that depend on the independent variables; they are the outcomes or results of the influence of the independent variables. Other names for dependent variables are criterion, outcome effect and response variables.
- Intervening or mediating variables stand between the independent and dependent variables and they mediate the effects of the independent variable on the dependent variable. For example if students do well on a research methods test (dependent variable),results may be due to (a) their study preparation (independent variable) and/or (b) their organization of study ideas into a framework (intervening variable) that influenced their performance on the test. The mediating variable the organization of study stands between the independent and dependent variables in the probable causal link.