Research MethodsUniversity of Massachusetts Boston
©2012 William Holmes1
A B?
Correlation is not Causation
Post Hoc fallacy“For Example” is not proofBelief is not theory
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Supporting EvidenceTemporal OrderingTheoryRejection of Rival Hypotheses
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Correlation between eventsCorrelation between
characteristicsData a result of research
having internal validity (not biased research)
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Potential outcomesObserved outcomesIndividual versus average
(expected) outcomesCompleters versus non-
completersStable Unit and Treatment
Value Assignment--SUTVA
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Cause precedes effectChronological ordering—
happenstance Conceptual ordering—theory Process ordering—empirical process
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Theoretical Assumptions of Program
SocialPsychologicalEconomicBiological
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Controlling Competing Influences—confounding variables
Control by Sampling--exclusionControl by Design--randomizationControl by Statistical Procedures--
controlling
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V=ViolenceSA=Substance
AbuseD=Depression
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The rival hypotheses: violence causes depression vs. substance abuse causes depression
V=ViolenceSA=Substance
AbuseD=Depression
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Indirect effects between violence and depression
V=ViolenceSA=Substance
AbuseD=Depression
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Spurious correlationbetween violence and depression
V=ViolenceSA=Substance
AbuseD=DepressionG=Genetics
Effect is conditional on other variable
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G
History—external to experimentMaturation—developmental changeInstrumentation—biased measuresSubject-Experiment Interaction—
persons messing with the experimentTesting Effects—persons learning from
the experiment
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Level of Measurement
Measures of Association
Test of Significance
Nominal/categorical
Percentage, Odds Ratio, Logit, Phi
t, Chi-square
Mixed Percentage, Means, Eta
t, F
Interval/Ratio Correlation, Regression
t, F
Determine presence of relationship--significance test or substantive criteria
Determine strength of relationship--measure of association
Compare bivariate results with what happens when controls are introduced
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