CAUSAL-COMPARATIVE RESEARCH

By: Brita Groves

OBJECTIVES• Explain what is meant by the term “causal-comparative

research.”• Describe how causal-comparative research is both similar to

and different from both correlational and experimental research.

• Identify and describe the steps involved in conducting a causal-comparative study.

• Look at a diagram of a design for a causal-comparative study.

• Describe some of the threats to internal validity that exist in causal-comparative studies and discuss how to control for these threats.

• Recognize a causal-comparative study when you come across one in the educational research literature.

What is causal-comparative research?

• Also known as “ex post facto” research. (Latin for “after the fact”).

• In this type of research investigators attempt to determine the cause or consequences of differences that already exist between or among groups of individuals.

In other words…

• Causal-comparative research is an attempt to identify a causative relationship between an independent variable and a dependent variable.• The relationship between the independent

variable and dependent variable is usually a suggested relationship (not proven) because you (the researcher) do not have complete control over the independent variable.

You are a first year agricultural education teacher at the local high school. At the state CDE contest you run into a Billy Bob (a fellow agricultural education teacher). When Billy asks how your year is going, you tell them that you are discouraged because your students do not seem to like your teaching very much and complain about your style of testing.

Billy Bob tells you that they have been using e-moments and some of the concepts from the FFA Life Knowledge materials to teach their classes. They think that their students really enjoy their teaching and are learning more because of it.

You wonder if Billy Bob’s approach would work for you…

• An appropriate way to approach this situation would be with a causal-comparative study.• You (the researcher) observe that 2 groups differ

on some variable (teaching style) and then attempt to find the reason for (or the results of) this difference.

***Note that the difference has already occurred.***

The Three Types

• There are 3 types of causal-comparative research:• Exploration of Effects• Exploration of Causes• Exploration of Consequences

Similarities to correlational research• Both types of research are examples of

associational research:• Researchers seek to explore relationships among

variables.

• Both attempt to explain phenomena of interest.

• Both seek to identify variables that are worthy of later exploration

• Often provide guidance for later experimental studies.

Similarities to correlational research

• Neither allow the researcher to manipulate the variables.

• Both attempt to explore causation.

Differences

Causal-Comparative• Typically compare 2 or

more groups of subjects

• Involves at least 1 categorical variable.

• Analyzes data by comparing averages or uses crossbreak tables.

Correlational• Requires a score on each

variable for each subject.

• Investigate 2 or more quantitative variables.

• Analyzes data by using scatterplots and/or correlation coefficients.

Similarities to experimental research

• Both require at least one categorical variable.

• Both compare group performances to determine relationships.

Differences

Causal-comparative• No manipulation of the

variables.

• Provide weaker evidence for causation.

• The groups are already formed, the researcher must find them.

Experimental• The independent variable is

manipulated.

• Provide stronger evidence for causation.

• The researcher can sometimes assign subjects to treatment groups.

The steps…

• Problem Formulation• Select the sample of individuals to

be studied.• Instrumentation- achievement

tests, questionnaires, interviews, observational devices, attitudinal measures…there are no limits…

The design

• The basic design is to select a group that has the independent variable and select another group of subjects that does not have the independent variable.

• The 2 groups are then compared on the dependent variable.

Internal Validity

• Usually 2 weaknesses in the research:• Lack of randomization• Inability to manipulate an independent

variable

• Threats• Oftentimes subject bias occurs• Location• Instrumentation• Loss of subjects

Data Analysis

• Construct frequency polygons.• Means and standard deviations

(only if variables are quantitative)• T-test for differences between

means.• Analysis of covariance

Proceed with caution!!!

• The researcher must remember that demonstrating a relationship between 2 variables (even a very strong relationship) does not “prove” that one variable actually causes the other to change in a causal-comparative study.

Limitations of Use

• There must be a “pre-existing” independent variable• Years of study, gender, age, etc.

• There must be active variables- variables which the research can manipulate • The length and number of study

sessions, instructional techniques, etc.

Examples

• Exploration of effects caused by membership in a given group.• Question: What differences in abilities

are caused by gender?• Hypothesis: Females have a greater

amount of linguistic ability than males.

Examples

• Exploration of causes of group membership.• Question: What causes individuals to

join a gang?• Hypothesis: Individuals who are

members of gangs have more aggressive personalities than individuals who are not members of gangs.

Examples

• Exploration of the consequences of an intervention.• Question: How do students taught by the

inquiry method react to propaganda?• Hypothesis: Students who were taught by

the inquiry method are more critical of propaganda than are those who were taught by the lecture method.

Example

• A Comparison of Urban Teacher Characteristics for Student Interns Placed in Different Urban School Settings

• Classroom Behavior of Good and Poor Readers

Chapter in Book

• Chapter 16• Pages 369 to 395• Summary on pages 393 to 394

References

• Fraenkel, J. (2006). How to design and evaluate research in education. (pp. 369-395). New York, NY: McGraw-Hill.

• McKinney, S. (2004). A comparison of urban teacher characteristics for student interns placed in different urban school settings. The

professional educator, 26(2).• Wasson, B. (2001). Classroom behavior of good and

poor readers. The professional educator, 23(3). • www.mnstate.edu/wasson/ed603/ed603lesson12.htm• www.faculty-staff.ou.edu/B/Nancy.H.Barry-1/cause.html