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Analysis of Professional Literature
Class 4:
QUANTITATIVE RESEARCH DESIGNS:
Experimental, Quasi-Experimental, & NonExperimental
Introduction
Having developed your research question, identified
a reading list, and planned the outline for your
literature review, we are now going to move on to
look at quantitative research design. What you
should keep in my mind is that there are two key,
current applications for developing your knowledge
about quantitative research design:
(i) to look at how your research question can be
examined through a variety of different designs;
(ii) to understand and describe the research designs
used in the empirical literature which you are
reading for your literature review.
Quantitative Research Designs:
Experimental, Quasi-Experimental, and NonExperimental
Quantitative research is commonly used to
investigate research questions. There is a potentially
infinite array of possible quantitative research
designs, and in the human sciences particularly, it
can be difficult to do pure, experimental research.
Thus a great many adaptations of experimental
designs, called quasi-experimental and nonexperimental designs have been developed. It is
important to consider a range of possible
quantitative research designs and their strengths
and weaknesses, before adopting any particular
design.
James Neill
Last updated:
Factors Jeopardizing Internal and External
Validity
(based on Campbell and Stanley (1963)
Campbell and Stanley (1963) define internal
validity as the basic requirements for an experiment
to be interpretable - did the experiment make a
difference in this instance? External validity
addresses the question of generalizability - to
whom can we generalize this experiment's findings?
Eight extraneous variables can interfere with internal
validity:
1. History, the specific events occurring between
the first and second measurements in addition to the
experimental variables
2. Maturation, processes within the participants as
a function of the passage of time (not specific to
particular events), e.g., growing older, hungrier,
more tired, and so on.
3. Testing, the effects of taking a test upon the
scores of a second testing.
4. Instrumentation, changes in calibration of a
measurement tool or changes in the observers or
scorers may produce changes in the obtained
measurements.
5. Statistical regression, operating where groups
have been selected on the basis of their extreme
scores.
6. Selection, biases resulting from differential
selection of respondents for the comparison groups.
7. Experimental mortality, or differential loss of
respondents from the comparison groups.
8. Selection-maturation interaction, etc. e.g., in
multiple-group quasi-experimental designs
Four factors jeopardizing external validity or
representativeness are:
9. Reactive or interaction effect of testing, a
pretest might increase
10. Interaction effects of selection biases and the
experimental variable.
11. Reactive effects of experimental
arrangements, which would preclude generalization
about the effect of the experimental variable upon
persons being exposed to it in non-experimental
settings
12. Multiple-treatment interference, where
effects of earlier treatments are not erasable.
Cook & Campbell's Method for Depicting
Research Designs
 X = exposure of a group to an experimental
variable or event, the effects of which are to be
measured
 O = some process of observation or
measurement
 Xs and 0s on the same line are applied to the
same specified persons
 Read left to right to indicate temporal order of
events (Xs and Os vertical to one another occur
simultaneously)
 R = randomized selection/allocation