Causal-Comparative Design

Comparisons with Correlational Research

Many similarities exist between causal-comparative research and correlational research. Both methods are useful when experimental research has been deemed impossible or unethical as the research design for a particular question. Both causal-comparative and correlational research designs attempt to determine relationships among variables, but neither allows for the actual manipulation of these variables. Thus, neither can definitively state that a true cause-and-effect relationship occurred between these variables. Finally, neither type of design randomly places subjects into control and experimental groups, which limits the generalizability of the results.

Despite similarities, there are distinct differences between causal-comparative and correlational research designs. In causal-comparative research, the researcher investigates the effect of an independent variable on a dependent variable by comparing two or more groups of individuals. For example, an educational researcher may want to determine whether a computer-based ACT program has a positive effect on ACT test scores. In this example, the researcher would compare the ACT scores from a group of students that completed the program with scores from a group that did not complete the program. In correlational research, the researcher works with only one group of individuals. Instead of comparing two groups, the correlational researcher examines the effect of one or more independent variables on the dependent variable within the same group of subjects. Using the same example as above, the correlational researcher would select one group of subjects who have completed the computer-based ACT program. The researcher would use statistical measures to determine whether there was a positive relationship between completion of the ACT program and the students’ ACT scores.

Comparisons with Experimental Research

A few aspects of causal-comparative research parallel experimental research designs. Unlike correlational research, both experimental research and causal-comparative research typically compare two or more groups of subjects. Research subjects are generally split into groups on the basis of the independent variable that is the focus of the study. Another similarity is that the goal of both types of research is to determine what effect the independent variable may or may not have on the dependent variable or variables.

While the premises of the two research designs are comparable, there are vast differences between causal-comparative research and experimental research. First and foremost, causal-comparative research occurs after the event or action has been completed. It is a retrospective way of determining what may have caused something to occur. In true experimental research designs, the researcher manipulates the independent variable in the experimental group. Because the researcher has more control over the variables in an experimental research study, the argument that the independent variable caused the change in the dependent variable is much stronger. Another major distinction between the two types of research is random sampling. In causal-comparative research, the research subjects are already in groups because the action or event has already occurred, whereas subjects in experimental research designs are randomly selected prior to the manipulation of the variables. This allows for wider generalizations to be made from the results of the study.

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