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MBA724 s6 w1 experimental design

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MBA724 s6 w1 experimental design

  1. 1. Experimental Design Learning Objectives Define experimentationExplain pros and cons of the experimental method Become familiar with key design principles of experiments Define internal validity Define external validity
  2. 2. ExperimentsManipulation of one variable to determine itseffect on other variablese.g. the impact of insurance plan (hasinsurance vs. no insurance) on auto repairquotee.g. the design of suspect identification(line-up vs. one by one) on eyewitnessaccuracy
  3. 3. Correlation ≠ Causation 6-3
  4. 4. Causation and Experimental Design Control/ Random Matching Assignment 6-4
  5. 5. Evidence of Causality Covariation between A and B Time order of events No other possible causes of B
  6. 6. Classic Experiment Strategy• Pre-test• Control group
  7. 7. Non-ExperimentsAfter-Only Case Study “Let’s do something and see what happens” X O
  8. 8. How much the researcher manipulates andcontrols the independent variables None – observations, document analysis, case studies*, surveys* Little – ex post facto experiments (or quasi- experiments) Full control – experiments*Surveys and case studies can be experimental depending on whether researcher manipulation is introduced
  9. 9. Conducting an Experiment Specify treatment variables Specify treatment levels Control environment Choose experimental design
  10. 10. Validity in Experimentation Internal External
  11. 11. Experiments – Pros and ConsAdvantages Disadvantages• Ability to manipulate IV •Artificiality of labs• Use of control group •Non-representative• Control of extraneous sample variables •Expense• Replication possible •Focus on present and• Field experiments immediate future possible •Ethical limitations
  12. 12. Discussion If your group were to address your research questions using the experimental methodology, how would you design the experiment? Discuss the following:  Independent variable(s)? (also called manipulation)  Dependent variable(s)? (also called outcome variables)  Confounding variable(s)? (potential alternative explanations)  Extent of control: full experiment or ex post facto?  Would you prefer a lab or field experiment?  How would you achieve random assignment?  How do you ensure blindness (or double-blindness?)  How do you make sure it’s not just a non-experiment? (e.g., an after-only case study)
  13. 13. -- End –Questions?

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