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Lecture 8

Lecture 8.docx

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Connie Boudens

Additional research designs Prof’s Speech – Purple Text Quasi-Experiments • Less control of extraneous variables • Usually random assignment is missing; the groups are naturally occurring • Doesn’t meet all the requirements for an experiment but has the nature of an experiment • Sometimes called a field experiment Some common features of quasi-experiments: • matching instead of randomization • time series analysis • unit of analysis: not people – may be a group, organization, program, etc. One Group Pre-post Threats to Internal Validity  History o The event affects the study outcome  Pre- and post- circumstances differ  Maturation o Change in subjects over time – differences can be based simply on age  Testing / Repeated testing o can cause subjects to be more aware of their behaviour/make them want to change their behaviour in subsequent tests  Mortality o people dropping out of the study o certain types of people dropping out, will not make a difference to the study o but other types can hinder the study  Regression to the mean o High or low maintenance measurements followed by measurements closer to the group mean Non -equivalent control group design - With control group - Selection bias – pre-existing differences between groups Time Series Analyses - Can’t randomize participants, but can get assignments of the dependent variable, pre- and post-treatment Single-Case Research Designs • Use only one case or group to investigate a specific phenomenon. • Not the same as a case study. • Uses time-series design. • Take multiple pre and post-treatment measures. Advantage of Small-N Design • Participants from hard to find populations • Results easy to interpret (often no stats) • Can focus on helping one (few) participant(s) A-B-ADesign - Baseline-treatment-baseline - Problems: might not be able to end with the baseline condition because the effect may not be reversible - Has a control group Multiple Baseline Design • Testing a treatment effect when the effect is irreversible. • Baseline data collected on: • 2 or more behaviours for same individual • Same behaviour for 2 or more individuals • Same behaviour across 2 or more situations for the same individual. Choosing a Research Method - All research methods have advantages and disadvantages - There is no one perfect method for everything - Different methods are better suited for different experiments The choice is affected by: • Resources like time and money • Ethical concerns – certain topics of study, i.e. child abuse, will have to greatly consider ethics) • The research question should guide the choice of method Description: asking what or how many, getting ideas about why, developing theory/How does the research question guide the choice? • Case study for unusual cases • Ex. Nonverbal children, natural disaster, hostage-taking situations • These circumstances cannot be created (because of ethical concerns) • Case study for in-depth examination • Ex. Merger of 2 companies • Correlational study Prediction: if I know X, can I predict Y? • Correlational study Causal: Verifying the why or how - Ex. Does drug X lead to the relief of symptom Y? • Experiment, quasi-experiment, field experiment **Chart  External validity ------------------------------------------- Internal validity  Observation/Measurement Experiments Simple Description Correlational St. Quasi Experiments “True” Experiments Qualitative Quantitative Explore Relate measured Test hypotheses in Test specific the Describe a variables to each naturally occurring hypotheses in process of behaviour/social other to test the events or field controlled “lab” trend hypothesis studies conditions behaviour Analyzing your results The type of data determines how you can analyse it. The type of analysis determines whether or not y
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