Week_9_single_case_qual1 - ScWk 240 Research Methods and...

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ScWk 240 Edward Cohen Page 1 ScWk 240 Research Methods and Design Week 9 October 24, 2008 San José State University Edward Cohen, Ph.D. Today: For next week: Readings for Week 9 (10/24) Lit Review check in Quasi-experimental time series designs Single case design Introduction to qualitative research Quasi-Experimental Time Series Designs A. Review your list of group designs to answer the following: 1. A researcher gathers a convenience sample of adolescents in a group home to try an intervention designed to reduce behavioral outbursts—a new group therapy focused on anger management. First the researcher measures the number of outbursts for 10 weeks before the intervention, then begins the group, and then measures the number of outbursts for 10 weeks after the group starts. 2. In the same group home, the researcher divides the adolescents into two groups—the first group gets the new group therapy, and the second group receives the standard counseling already provided. Both groups are matched on length of time in the group, severity of behavioral problems, gender, and ethnicity. The measurement strategy is the same as in #1. 3. Name two threats to internal validity that can be addressed by #2 to improve the research design from #1. B. Simple and Interrupted Time Series (Quasi-Experimental Design) 1. A simple time series is a longitudinal design with multiple, repeated observations or measurements. Example: one-year stock price chart. 2. An interrupted time series design is used to evaluate treatment or the effects policy or environmental phenomena on the dependent variable 3. For the interrupted time series design, the main question is “is the trend of the data line affected by the intervention, or by other rival hypotheses?” 4. The quasi-experimental time series design allows you to analyze trends in observations that can help rule out effects of history, maturation, or other reasons why the “trend line” might have patterns that have nothing to do with the treatment
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ScWk 240 Edward Cohen Page 2 5. Time series plots can be analyzed visually, but often have to be statistically analyzed when (more typically) the visual plot is ambiguous Single Case Designs (also known as Single System Designs) I. What is a “single case design”? – a time series design used to evaluate the impact of an intervention or a policy change on an individual case (can be a person, a county, a city, etc.) II. Why do a single case design? A. You can evaluate an intervention in a clinical setting when you don’t have access to large sample size—even with just one research participant B. A single case study is a good design to use when evaluating the implementation of an already-tested intervention at a community agency C. Single case design method--Single case designs use the single interrupted time series O pre1 , O pre2 , O
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Week_9_single_case_qual1 - ScWk 240 Research Methods and...

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