EDUCATIONAL RESEARCH: CAUSAL-COMPARATIVE STUDIES

Nasih Jaber Ali 25-10-2011

THE BASIC STEPS OF RESEARCH...

Scientific and disciplined inquiry is an orderly process, involving:

Recognition and identification of a topic to be studied (“problem”)

Description and execution of procedures to collection information (“method”)

Objective data analysis

Statement of findings (“results”)

RESEARCH METHODS...

Quantitative…

Collects and analyzes numerical data obtained from formal instruments

QUANTITATIVE METHODS...

Descriptive research (“survey research”)

Correlational research Causal-comparative research (“ex post

facto research”)

Experimental research

CAUSAL-COMPARATIVE RESEARCH (“EX POST FACTO RESEARCH”)

At least two different groups are compared on a dependent variable or measure of performance (called the “effect”) because the independent variable (called the “cause”) has already occurred or cannot be manipulated

RESEARCH VARIABLES...

Independent… An activity of characteristic believed

to make a difference with respect to some behavior

experimental variable, cause, treatment

DEPENDENT VARIABLE…

The change or difference occurring as a result of the independent variable

criterion variable, effect, outcome, posttest

A CAUSAL-COMPARATIVE STUDY…

A study in which the researcher attempts to determine the cause, or reason, for pre-existing differences in groups of individuals…. called an “ex post facto” study because both the effect and the alleged cause have already occurred and must be studied in retrospect

DIFFERENCES IN CAUSAL-COMPARISON AND CORRELATIONAL STUDIES…

Causal-comparative studies… * attempt to identify cause-effect

relationships Correlational studies… * attempt to identify relationships

Causal-comparative studies…

* involve two (or more) groups and one independent variable

Correlational studies… * typically involve two (or more)

variables and one group

Causal-comparative studies…

* involve making comparisons

Correlational studies…

* involve establishing relationships

DIFFERENCES IN CAUSAL-COMPARISON AND EXPERIMENTAL STUDIES…

Causal-comparative studies… * individuals are not randomly

selected but selected because they belong to groups

Experimental studies… * individuals are randomly selected

and assigned to two (or more) groups

Causal-comparative studies…

* the researcher cannot manipulate the independent variable

Experimental studies…

* the researcher manipulates the independent variable

Causal-comparative studies… * the independent variable has

already occurred and cannot be manipulated

Experimental studies… * the researcher manipulates the

independent variable to determine its effects

CONDUCTING A CAUSAL-COMPARATIVE STUDY…

1. Select the problem2. Select participants and instrument3. Design and procedure4. Data analysis and interpretation

1. SELECT THE PROBLEM…

* The researcher starts with an effect and seeks its causes

* The independent variable cannot or should not be manipulated

2. SELECT THE PARTICIPANTS AND INSTRUMENT

* Select samples representative of their respective populations and similar with respect to critical variables other than the independent variable

* called “comparison groups”

3. DESIGN AND PROCEDURE…

* The performance of the groups is compared using some valid dependent variable measure (“instrument”)

* Lack of randomization, manipulation, and control are sources of weakness

CONTROL

* The process by which the researcher attempts to ensure that the findings are as free of researcher bias and error as possible

• TYPES OF CONTROL

* Random assignment of participants to groups

* Pair-wise matching* Comparing homogeneous groups* Comparing homogeneous subgroups* Factorial analysis of variance* Analysis of covariance

• RANDOM ASSIGNMENT OF PARTICIPANTS TO GROUPS

* Not possible in causal-comparative studies because the groups already exist and have already received the treatment

• PAIR-WISE MATCHING

* First: find a participant in the second (third, fourth, etc.) group with the same or similar score on the control (non manipulated) variable as the participant in the first group

* Second: if a participant in either group does not have a suitable match, the participant is eliminated from the study

COMPARING HOMOGENEOUS GROUPS

* Control for extraneous variables that are homogeneous with respect to the extraneous variables

* Limitation: lowers the number of participants in the study and, of course, limits the generalizability of the findings

• COMPARING HOMOGENEOUS SUBGROUPS

* Form subgroups within each group that represent all levels of the control (non manipulated) variable

* Controls for the variable and also permits the researcher to determine whether the independent variable affects the dependent variable differently at different levels of the control (non manipulated) variable

• FACTORIAL ANALYSIS OF VARIANCE

* Building the control (non manipulated) variable into the research design

* Then use factorial analysis of variance to analyze the results to determine the effect of the independent and control (non manipulated) variable on the dependent variable, both separately and in combination

Factorial analysis of variance Allows the researcher to determine if there is an interaction between the independent variable and the dependent variable such that the independent variable operates differently at different levels of the independent variable building it into the research design

• ANALYSIS OF COVARIANCE (“ANCOVA”)

* Statistically adjusts initial group differences on a dependent variable for initial differences on some other variable related to performance on the dependent variable

* Removes initial differences so that the results can be fairly compared as if the two groups started equally

4. DATA ANALYSIS AND INTERPRETATION

* Researcher uses a variety of descriptive and inferential statistics:

MeanStandard deviationt-testAnalysis of variance

• MEAN* The descriptive statistic indicating the

average performance of an individual or group on a measure of some variable

• STANDARD DEVIATION

* The descriptive statistic indicating the spread of a set of scores around the mean

• T-TEST

* The inferential statistic indicating whether the means of two groups are significantly different from one another

• ANALYSIS OF VARIANCE (“ANOVA”)

* The inferential statistic indicating the presence of a significant difference among the means of three or more groups

REFERENCES

Jack R. Franenkel, Norman E. Wallen. How to design and evaluate research in education

Louis Cohen, Lawrence Manion. Research methods in education