This document provides an overview of quantitative research design. It defines quantitative research as the systematic investigation of numerical data to explain phenomena through statistical analysis and testing of theories. The key aspects covered include: variables are the basic building blocks and can be categorical or quantitative; variables can be independent, dependent, mediating or moderating; experimental research involves manipulating the independent variable while non-experimental research observes relationships; correlational research examines relationships between variables; and ex post facto research investigates causes retrospectively when manipulation is not possible. Experimental, quasi-experimental, single-case and meta-analysis are also discussed as research methods.

1. Quantitative ResearchQuantitative Research
DesignDesign
An OVERVIEWAn OVERVIEW

2. Quantitative Research:Quantitative Research:
• Systematic scientific investigation of data
and their relationships.
• The kind of research that involves the
tallying, manipulation, or systematic
aggregation of quantities of data.
(Grant Henning "Quantitative Methods In Language Acquisition
Research“)

3. Quantitative Research:Quantitative Research:
• The collection of numerical data in order to
explain, predict and/or control phenomena
of interest.
(L.R. Gay ”Educational Research: Competencies for Analysis and
Application”)

4. Quantitative Research:Quantitative Research:
• An inquiry into a social or human problem
based on testing a theory composed of
variables, measured with numbers, and
analyzed with statistical procedures, in
order to determine whether the predictive
generalizations of the theory hold true.
(John W. Creswell ”Research Design: Qualitative and Quantitative
Approaches”)

5. Overview of Quantitative ResearchOverview of Quantitative Research
• The objective of quantitative research is to
develop and employ mathematical
models, theories and hypotheses
pertaining to natural phenomena.
• Measuring is key in quantitative research
because it shows the relationship between
data and observation.

6. Quantitative Research MethodsQuantitative Research Methods
• The basic building blocks of quantitative
research are variables.
Variables are something that takes on
different values or categories.

7. Common Types of Variables Classified by Level ofCommon Types of Variables Classified by Level of
Measurement and by Role of VariableMeasurement and by Role of Variable
Variable Type Key Characteristic Example
Level of Measurement
Categorical
Variable
Made up of different
types or categories
of a phenomenon
Gender categories:
male and female
Quantitative
Variable
Varies in degree or
amount of a
phenomenon
Annual Income
varies from zero
income to very high
income level

8. Variable Type Key Characteristic Example
Role Taken by the Variable
Independent
Variable
Presumed to cause changes
to occur in another variable
(causal variable)
Amount of studying (IV) affects
test grades (DV)
Dependent
Variable
A variable that changes
because of another variable
(effect or outcome
variable)
Amount of studying (IV) affects
test grades (DV)
Mediating
Variable
(Intervening
Variable)
Comes in between other
variables, helps to delineate
the process through which
variables affect one another
Amount of studying (IV) leads
to input and organization of
knowledge in long-term
memory (mediating variable)
which affects test grades (DV)
Moderator
Variable
Delineates how a relationship
of interest changes under
different conditions or
circumstances
Perhaps the relationship
between studying (IV) and test
grades (DV) changes
according to the different levels
of use of a drug such as
Retalin (moderator variable)

9. Types of Quantitative researchTypes of Quantitative research
•EXPERIMENTAL RESEARCH
DESIGN
•NONEXPERIMENTAL RESEARCH
DESIGN

10. Experimental Research DesignExperimental Research Design
• The purpose of experimental research is
to study cause and effect relationships.
• Its defining characteristic is active
manipulation of an independent variable
(i.e., it is only in experimental research that
“manipulation” is present).
• Also, random assignment (which creates
"equivalent" groups) is used in the
strongest experimental research designs.

11. Correlational ResearchCorrelational Research
• To find if the data has an observable
relationship that can be further specified
in terms of magnitude and/or an increase
or decrease.

12. Characteristics of CorrelationalCharacteristics of Correlational
ResearchResearch
• Correlation indicates the strength and
direction of a linear relationship between
variables.

13. Correlation and SignificanceCorrelation and Significance
• Is there a relationship
between two
variables/data?
• What is the direction
of the relationship?
• What is the
magnitude?
• These relationships
may show any
tendency for the
variables to vary
consistently.
• Pearson’s product
moment coefficient
correlation: -1.0 to
+1.0

15. Ex post factoEx post facto
‘‘from what is done afterwards’from what is done afterwards’

16. • Studies that investigate possible cause
and effect relationships by observing an
existing condition or state of affairs and
searching back in time for plausible causal
factors.

17. Characteristics of Ex Post FactoCharacteristics of Ex Post Facto
• Researcher takes the effect/dependent
variable and examines it retrospectively
• Establishes causes, relationships or
associations and their meanings.
• Researcher has little to no control over
independent variables.
• Flexible by nature.

18. When to use this?When to use this?
• You can use this where more powerful
experimental designs are not possible;
when you are unable to select, control and
manipulate the factors necessary to study
cause and effect relationships directly, or
when control variables except a single
independent variable may be unrealistic
and artificial.

19. Ex post facto advantages andEx post facto advantages and
disadvantagesdisadvantages
Advantages
• Show a correlation where
more rigorous
experimentation is not
possible
• Exploratory tool
• Useful to avoid articiality
in the research.
• Shows cause and effect
relationships
Disadvantages
• Lack of control for
independent variable and
randomizing subjects.
• Never certain if causative
factor has been included
or identified
• Relationship between two
factors does not est.
cause and effect.
• May be regarded as too
flexible.

20. ExperimentalExperimental
• Research in which the investigator
deliberately controls and manipulates the
independent variable to observe the effect
of that change on another the dependent
variable.

21. How and when to useHow and when to use
Experimental ResearchExperimental Research
• Most commonly used in Educational
research.
• You vary the independent variable and
look for the effect it has on the dependent
variable.

22. How and When to use Quasi-How and When to use Quasi-
experimental researchexperimental research
• Used when you have control over the
“when and the whom of measurement”,
but lack control over the “when and to
whom of exposure.”
• Common in educational research.

23. How and when to use Single CaseHow and when to use Single Case
researchresearch
• Process of continuous assessment of
some aspect of human behavior over a
period of time.
• Involves “intervention effects”, that are
replicated in the same subject(s) over
time.
• Used in many fields including psychology,
education and social work.

24. How and when to use Meta-How and when to use Meta-
analysis researchanalysis research
• Research to explore the effectiveness of
classroom methods.
• Involves aggregating the results of other
studies into a coherent account.

25. Useful TermsUseful Terms
• Correlation- Indicates the strength and direction
of a linear relationship between two random
variables.
• Ex post facto- from the Latin for "from
something done afterward"
• Quasi- the prefix 'quasi' denotes methods that
are "almost" or "socially approximate"
• Variable- a measurable factor, characteristic, or
attribute of an individual or a system

26. ReferencesReferences
• Research Methods in Education 5th
Edition, Louis Cohen, Lawrence, Manion
and Keith Morrison 2004, New York
• http://en.wikipedia.org/wiki/Main_Page,
4/10/2007