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Alternative Approaches

Alternative Approaches. Specialized Designs. 1. Single Subject Designs. A is baseline. B is treatment. Add and remove treatment to find effect. Common designs: A-B, A-B-A, A-B-A-B. Interrupted Time Series. Effects of 9/11 on volunteering. 2. Quasi-experimental Designs.

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Alternative Approaches

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  1. Alternative Approaches Specialized Designs

  2. 1. Single Subject Designs A is baseline. B is treatment. Add and remove treatment to find effect. Common designs: A-B, A-B-A, A-B-A-B

  3. Interrupted Time Series Effects of 9/11 on volunteering

  4. 2. Quasi-experimental Designs • Quasi-experiments have treatment groups, but non-random assignment to treatment. E.g., classroom as group assignment in ed study. • Non-experimental or pre-experimental study: Single group pre-post study. Measure at T1, treat group, measure at T2. Effect? T1 T2 T1 T2 T1 T2 No causal conclusion is possible here.

  5. Quasi-experimental Design (2) • Pre-experimental design lacks a control group. Toothpaste & tooth loss. • Other examples? • Corporate training.

  6. Quasi-Experiment (3) • Nonequivalent control group design. Have pre-post measures for 2 groups, but no random assignment to group. Control is best match we can do. Note. Pretest means are different. Look for what would be an interaction in a true experiment.

  7. Quasi-experiment (4) • No treatment effect Means for both groups increase similarly.

  8. Review • How do you show an effect with a single-subject design? • How do you show an effect with a quasi-experiment? • What is the major design difference between a true experiment and a quasi experiment? • What is the difference in what you can infer between the true experiment and the quasi-experiment?

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