Causal-Comparative Research Designs Introduction

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

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

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)

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

Causal-Comparative Research Method Table 10.1 Academic Achievement and Extracurricular Participation of Employed and Nonemployed Students Employed Students Nonemployed t p Variable M 1. GPA 2.66 2.78 .81 .42 2. ACT score 17.13 18.93 2.22 .02 3. Extracurricular participation (hours per week) 6.21 8.93 .05

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

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”

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

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

Data Collection Standardized tests Questionnaires Interviews Naturalistic observations

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)