Causal-Comparative Research Designs

1. Causal-Comparative Research Designs

2. Causal-Comparative Research Method • The Study of Relationships between Variables • Educational research is done to DESCRIBE educational phenomena or to EXPLORE relationships between phenomena • The type of relationship of greatest interest to educators is that involving cause and effect • The discovery of cause-and-effect relationships is useful both for theory development and for educational improvement

3. Causal-Comparative Research Method • The Study of Relationships between Variables • Causal-comparative method is the simplest quantitative approach to exploring cause-and-effect relationships between phenomena • It involves a particular method of analyzing data to detect relationships between variables • The correlational method is another approach to achieve the same goal

4. Causal-Comparative Research Method • Advantages • AKA “ex post facto research” – causes are studied after they presumably have exerted their effect on another variable (e.g., administer a questionnaire to study the causes of high academic achievement) • Allows us to study cause-and-effect relationships under conditions where experimental manipulation is difficult or impossible • Many relationships can be studied in a single research study (refer to table 10.1)

5. Causal-Comparative Research Method • Disadvantages • Difficult to establish causality on the basis of the data collected • An observed relationship between variables A and B can mean that A causes B, B causes B, or a third variable C causes both A and B

6. Causal-Comparative Research Method Table 10.1 Academic Achievement and Extracurricular Participation of Employed and Nonemployed Students

7. Planning a Causal-Comparative Study • Statement of the Research Problem • Selecting a Defined Group • Selecting Comparison Groups • Data Collection • Data Analysis

8. Statement of the Research Problem • Speculate about the causes or effects of the phenomenon that interest you (i.e., based on previous research findings and theory, as well as your own observations of the phenomenon • After possible causes and effects have been identified, they should be incorporated into the statement of the research problem • Researcher should attempt to state and test alternative hypotheses about other factors that might explain observed differences between two groups • “Strong inference” vs. “shotgun approach”

9. Selecting a Defined Group • Define the group that possesses the characteristics one wishes to study • The definition should be precise so that the results of the study can be interpreted meaningfully

10. Selecting a Comparison Group • Once you have selected a group having the characteristic you wish to study, the next step is to select a group NOT having this characteristic, or having it to a lesser degree • The population from which the comparison sample is to be selected usually is defined so as to be similar to the characteristic-present group except for the variable being studied • Matching: used to equate two groups on one or more extraneous variable so that these extraneous variables do not confound study of causal relationships involving the variables of primary interest to the researcher • Extreme-groups method: involves selecting comparison groups that are at the two extremes of a score distribution on one variable

11. Data Collection • Standardized tests • Questionnaires • Interviews • Naturalistic observations

12. Data Analysis • Compute descriptive statistics for each comparison group in the study (e.g., group mean, stand deviation) • Conduct a test of statistical significance (choice of test depends research questions; t-test, ANOVA; MANOVA)