This document provides an overview of quantitative research design. It defines key terms and discusses the differences between experimental and non-experimental designs. Non-experimental designs include descriptive and correlational methods. Experimental designs manipulate a variable to measure its effect and can be true experiments or quasi-experiments. The document provides examples and discusses threats to validity.

1. Quantitative Research Design
Ken N. Meadows, Ph.D.
Educational Researcher
Teaching and Learning Services

2. Outline
 Defining quantitative research design
 Non-Experimental designs
 Descriptive
 Correlational
 Experimental designs
 Experiments
 Quasi-experiments
 Conclusions…
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3. Definitions
 Research design: the framework used to
conduct the research
 Research method: data collection techniques
(e.g., document analysis, interview, survey)
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4. Definitions
 Quantitative research2,6:
 Assumptions:
 Reality - objective & singular
 Researcher - independent from research
 Research - value-free, unbiased
 Research process – deductive (generate
hypotheses from theory), emphasize cause/effect,
isolation of variables, context-free, prediction,
generalizability
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5. Definitions
 Quantitative research2,6:
 Methods: larger scale (e.g., survey)
 Data: quantitative (numbers)
 Analysis: statistical
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6. Definitions
 Qualitative research2,6:
 Assumptions:
 Reality – subjective & multiple (from participants’
perspective)
 Researcher – interacts with research
 Research – value-laden, biased
 Research process – inductive (generate theory from
data), emergent variables (identified during
research), patterns identified
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7. Definitions
 Qualitative research2,6:
 Methods: smaller scale (e.g., interviews)
 Data: qualitative (words)
 Analysis: thematic
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8. Definitions
 Two broad categories of quantitative designs:
 Non-experimental
 Experimental
 A major difference - validity of the designs7
 Internal validity: extent design can identify causal
relationships & rule out alternate explanations of
relationships between variables
 External validity: extent design allows conclusions
to generalize beyond the confines of study
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9. Definitions
 Non-experimental designs tend to be low in
internal validity but higher in external validity
 Experimental designs tend to be high in internal
validity but lower in external validity
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10. Non-experimental
 Non-experimental designs:
 Descriptive
 Correlational
 Descriptive designs5,7 - identify the
characteristics of a phenomenon
 Describe the variable under investigation –
not examine relationships among variables
 For example: LARSN needs assessment
(Hoffman, Meadows, & Martin-Gardiner,
2009) 10

11. Non-experimental
 Correlational designs examine relationships
among variables under investigation1,5,7
 Tend to examine relationships as they exist
 Do not isolate & manipulate variables to
establish causal relationships as in
experimental research
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12. Non-experimental
 For example, Eron, Huesmann, Lefkowitz, &
Walder (1972) examined relationship
between preferences for violent television &
aggressive behaviour
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13. Non-experimental
 Cannot make causal statements with
correlational research1,5,7
 Directionality problem (if X <-> Y, does X ->Y or
Y ->X)
 Third variable problem (if X <-> Y, possible
X<-Z->Y)
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14. Non-experimental
 More complex correlational designs can
suggest direction of causality
 E.g., Cross-lagged panel correlation design
 Eron and colleagues (1972) – collected data
at grade 3 &13 and correlated variables
between years – found moderate correlation
between grade 3 preference for violent tv &
grade 13 aggressive behaviour
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15. Non-experimental
 In groups of 3, please discuss:
 Research question you would be interested in
researching
 Design of your research (i.e., descriptive or
correlational)

 Data sources for that project
 Research methods you would use
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16. Experimental
 Experimental designs:
 Experimental
 Quasi-experimental
 Experiment1,3,5,7 - variable is systematically
manipulated (independent variable; IV) to
observe effect of manipulation on another
variable (dependent variable; DV)
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17. Experimental
 Experimental control1,3,5,7 – hold extraneous
variables constant in experiment to isolate
effect of IV on DV
 For example, Hopkins & Wilson (2009)
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18. Experimental
 Common experimental design: pre-test/post-test
control group design1,3,5,7
Measure Exposure Measure
Before After
Treatment 01 X 02
Group
Control Group 03 04
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19. Experimental
 If change from pre- to post-test for treatment
group & not control group (or not as much),
change can be attributed to the treatment
(assuming proper experimental controls)
 Controlling for extraneous variables1,3,5,7:
 Participant differences: random assignment of
participants to treatment and control groups or
matching
 Situational differences: hold situations constant
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20. Experimental
 Pre-test/Post-test Control Group7 – possible pre-
test influences treatment (threat to external validity)
 Post-test only control design7:
Exposure Measure
After
Treatment X 01
Group
Control Group 02
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21. Experimental
 Post-test only control group – groups should
be same on DV before treatment because of
random assignment
 Other threats to external validity for
experiments8:
 Interaction effect of selection bias and treatment
 Reactive effects of the experiment
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22. Experimental
 Quasi-experimental designs5,8: not true
experiments because the groups tend to be
naturally occurring not groups created by
researcher
 Try to match participants and control for
situational variables as much as possible
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23. Experimental
 Common quasi-experimental design: pre-test/post-
test non-equivalent group design8
Measure Exposure Measure
Before After
Treatment 01 X 02
Group
Control Group 03 04
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24. Experimental
 Example: Haffie, Meadows, Dunn, & Graves
(2009)
 quasi-experimental research higher in
external validity than experiments (reflect real
life more) but weaker in internal validity than
experiments (do not control for all extraneous
variables) 8
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25. Experimental
 In groups of 3, please discuss:
 New research question you would be interested in
researching
 Design of your research (i.e., experimental or quasi-
experimental)

 Data sources for that project
 Research methods you would use
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26. Questions, comments…
kmeadow2@uwo.ca
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27. References
1. Bordens, K. S. & Abbott, B. B. (2008). Research design and
methods: A process approach (7th ed.). Boston: McGraw-Hill.
2. Creswell, J. W. (1994). Research design: Qualitative and
quantitative approaches. Thousand Oaks, CA: Sage Publications.
3. Elmes, D. G., Kantowitz, B. H., Roediger III, H. L. (1999).
Research methods in psychology (6th ed.). Pacific Grove, CA:
Brooks/Cole Publishing Company.
4. Eron, L. D., Huesmann, L. R., Lefkowitz, M. M. & Walder, L. O.
(1972). Does television violence cause aggression? American
Psychologist, 27, 253-263.
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28. References
5. Leedy, P. D., & Ormrod, J. E. (2001). Practical research: Planning
and design (7th ed.). Upper Saddle River, N.J.: Merrill Prentice
Hall.
6. O'Leary, Z. (2004). The essential guide to doing research. London:
Sage.
7. Powell, R. R., & Connaway, L. S. (2004). Basic research methods
for librarians (4th ed.). Westport, Conn.: Libraries Unlimited.
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