Choosing Research Designs I
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Transcript of Choosing Research Designs I
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Choosing Research Designs I
Experimental and Quasi-Experimental
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Experimental Designs•Experimental research design: The researcher has control over the experiment in terms of sample selection, treatment, environment, etc.
•Experimental designs are typical in psychology, medicine, education, etc.
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Experimental DesignsExperiments often discuss pre and post test observations
• POST-TEST ONLY
X O 1
Where:0t = Observation in time t of experimental group X = Treatment 0c = Control group
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Experimental Designs• PRE-TEST POST-TEST
O1 X O2
Note how the above test includes no control group. What is a control group and why include it?
• PRE-TEST POST-TEST WITH CONTROL GROUP
O1 X O2
O1 O2
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Key question of Internal ValidityKey question of Internal Validity• When we test a hypothesis and either
accept it or reject it, how do we know that we made the right decision?
• What about alternative explanations that we did not account for?
• What should we do to gain confidence?
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Internal ValidityInternal Validity• Are there other causes for what I am
observing?
• If so, a study will lack internal validity if it cannot rule out plausible alternative explanations.
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Internal Validity of a StudyInternal Validity of a Study
• What you measured and what you saw?
• Your program and your observations?
ObservationObservation
Research ProjectResearch Project ObservationsObservationsWhat you What you dodo What you What you seesee
Is the relationship Is the relationship causalcausal between... between...
AlternativeAlternativecausecause AlternativeAlternative
causecause
AlternativeAlternativecausecause
AlternativeAlternativecausecause
In In thisthis study study
Program-outcome RelationshipProgram-outcome Relationship
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•DID YOU FIND THAT BORING?
THEN HOW ABOUT A JOLT OF CUTENESS!
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Experimental Designs• What do you do if you fear that your
simple pre and post test single observations are atypical?
• CONTROL WITH MORE OBSERVATION IN THE PRETEST
O1 O2 O3 X O4
O1 O2 O3 O4
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Experimental Designs• Of course, we could also experiment
to see if removing a factor has an effect instead of adding a treatment factor
• PRE-TEST POST-TEST REMOVING THE TREATMENT
_O1 X O2 X O3 X 04
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Experimental DesignsResearch design with more power to control
for time
• Pre-test post-test
O1 O2 O3 X O4 O5 O6
• Pre-test post-test with control group
O1 O2 O3 X O4 O5 O6
O1 O2 O3 O4 O5 O6
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Did you bring your lab coat?• Considering true experiments are
close to impossible or unethical in political science, we need to apply science differently.
• Hence, this is why we in political science often use Quasi-experimental or non-experimental research designs
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Quasi-Experimental• Quasi-experiments: The researcher
does not have control over the experiment, rather the experiment occurs in a “natural” setting.
• Quasi-experimental design are typical in economics, sociology, public administration, urban planning, political sciences, etc.
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Quasi-Experimental• A prominent example of this type of research is arguably by Samuel Huntington, who argues that Latin American immigration, especially Mexican, is altering US culture for the worse.
• He essentially predicts that the United States will be a divided, less productive, society, ruining the past culture that has made the United States great.
http://www.foreignpolicy.com/story/cms.php?story_id=2495
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Quasi-ExperimentalHuntington points out the following X variables:
• Proximity of Mexico, Latin America to USA• Former ties to Mexico• Magnitude of recent wave of immigration• Duration of recent wave of immigration• Illegality
He does this by observing what is going on today. It is crucial that one understands his assumptions and evaluates what he claims as evidence for his theory