quasi-experimental designs -...
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Quasi-Experimental DesignsSay goodbye to Factorial designs and ANOVAsMove on to
QuasiQuasi--Experimental DesignsExperimental DesignsCase StudiesNaturalistic ObservationInterviews/Narratives/Focus GroupsSurvey ResearchAnalyses: Chi Square, Correlations, Multiple
regressions
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Quasi-Experimental Designs
“Static” variables: Experimenter does not manipulate
Therefore all could be subject to unknown or unanticipated confounds
Cannot clearly isolate cause and effectDefined in terms of correlations of
associationsIn an article, preferred description is the
strength of the association
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Quasi-Experimental DesignsCase studies: Useful as an example or to
highlight some unusual circumstanceProblems: Not systematic, no comparison group
Naturalistic Observation: Useful in helping to guide future research, guiding/shaping theoryProblems: Unobtrusive? What behaviors should be observed?Validation of observed behaviors?
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Quasi-Experimental Designs
Interviews/Narratives/Focus GroupsCan be useful as part of a program of
research. People can talk about “meaning” and “importance”
Problems: Again, defining and validating behaviorsDeciding on specific behaviors/topicsUnobtrusiveness of moderator?
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Quasi-Experimental DesignsSurvey research: Complicated, so we will
cover this on WednesdayAnalyses:
Chi squareCorrelationMultiple regressionPath analysisStructural Equation Modeling (SES)Odds Ratios, etc.
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Quasi-Experimental Designs
Most important point to remember:
All measure the strength of association and cannot show cause/effect. Only a true experiment can show that.
Very useful as part of a program of research
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Quasi-Experimental Designs
Survey research more than other type of research
Most often used,
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Quasi-Experimental Designs
Survey research more than other type of research
Most often used, Most often mishandled,
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Quasi-Experimental Designs
Survey research more than other type of research
Most often used, Most often mishandled,Most often misunderstood,
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Quasi-Experimental Designs
Survey research more than other type of research
Most often used, Most often mishandled,Most often misunderstood,Most often manipulated
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Quasi-Experimental Designs
Survey researchAs with other quasi-experimental designs:Measure “static” variables
You do not manipulate, nature doesExamples?
Association between two or more variables is the best you can do
No cause/effect
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Quasi-Experimental Designs
Why used?Ease of useSome variables cannot be manipulatedHelpful pre-experimental design
Several issues need to be attended to:
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Quasi-Experimental Designs
Obtaining a representative sampleEffects of method of contact and
assessmentQualities of survey instrument itselfThreats to internal validity
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Quasi-Experimental Designs
Obtaining a representative sampleRepresentative of what? Whom?How do you find them?How do you maximize participation?
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Quasi-Experimental DesignsEffects of method of contact and assessmentTelephoneLetters (snail mail, e-mail)Advertisement (Newspapers, flyers, web)Word of mouthConvenience sampleAssessment: Face to face? Oral/written?
Telephone? Internet? Other?By whom? What language?How might these affect responses?
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Quasi-Experimental Designs• Qualities of survey instrument itself• Avoid “homegrown” including altering an
existing instrument as little as possible• Look for instrument with good
psychometric data and carefully assess and report your psychometric data
• Psychometric data: Reliability, validity, standardization
• Self-report vs. other report?• Length? Reading level? Clarity? Scale
used? Other qualities?
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Quasi-Experimental Designs• Developing a survey instrument• Examples: Forced choice, dichotomous
responses, Likert scale, nominal responses
• Question: How do the responses “group together”?
• Internal reliability• Factor analysis• Whole area of study in itself
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Quasi-Experimental Designs• Survey research:• Threats to internal validity• Selection
• Example: DUI study men vs women• Berksen’s bias
• Mortality• Failure to complete or respond (e.g. rate of
return)• Selection X Mortality
• Failure to complete at a differential rate
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Quasi-Experimental Designs• How to report in APA style• Always report as an association• Could be predictor but only if
theoretically sound and use proper controls
• Correlations, multiple regressions etc. on Friday
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Quasi-Experimental Designs• Correlation• Association between two variables• Positive vs. Negative• Effects of increase in number of
participants• Effects of large number of correlations
with same data set (Bonferroni corrections)
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Quasi-Experimental Designs
• Multiple Regression: How do a set of variables interact to predict criterion or outcome variable?
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Quasi-Experimental DesignsExample: Predicting GPAPredictor variables—
Parental variablesPast GPASubject variables (e.g. age, sex)SESOther variables?
Independent and interactive contributionsModels (Equations)Stepwise versus Hierarchical regression
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Quasi-Experimental Designs
Logistical Regression: Criterion variable is dichotomous rather than continuous
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Quasi-Experimental Designs
Logistical Regression: Criterion variable is dichotomous rather than continuous
Path analysisTheory: X leads to Y, Y leads to Z
Extension of Multiple regression techniques over time
Models (theory) reflect the time element
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Quasi-Experimental DesignsMany types of Research designs beyond the
scope of this courseRight now, reading and understanding
research is the goalTo learn more, take more courses, get
involved in research (DIS opportunities), read books and articles
Psychology is a research-based discipline