Choosing Research Designs I Experimental and QuasiExperimental Experimental
- Slides: 15
Choosing Research Designs I Experimental and Quasi-Experimental
Experimental Designs • Experimental research design: The researcher has control over the experiment in terms of sample selection, treatment, environment, etc. • Experimental designs are typical in psychology, medicine, education, etc.
Experimental Designs Experiments often discuss pre and post test observations • POST-TEST ONLY X O 1 Where: 0 t = Observation in time t of experimental group X = Treatment 0 c = Control group
Experimental Designs • PRE-TEST POST-TEST O 1 X O 2 Note how the above test includes no control group. What is a control group and why include it? • PRE-TEST POST-TEST WITH CONTROL GROUP O 1 X O 2
Key question of Internal Validity • When we test a hypothesis and either accept it or reject it, how do we know that we made the right decision? • What about alternative explanations that we did not account for? • What should we do to gain confidence?
Internal Validity • Are there other causes for what I am observing? • If so, a study will lack internal validity if it cannot rule out plausible alternative explanations.
Internal Validity of a Study Is the relationship causal between. . . • What you measured and what you saw? • Your program and your observations? Alternative cause Research Project What you do Observation Program-outcome Relationship Observations What you see Alternative cause In this study
• DID YOU FIND THAT BORING? THEN HOW ABOUT A JOLT OF CUTENESS!
Experimental Designs • What do you do if you fear that your simple pre and post test single observations are atypical? • CONTROL WITH MORE OBSERVATION IN THE PRETEST O 1 O 2 O 3 X O 4
Experimental Designs • Of course, we could also experiment to see if removing a factor has an effect instead of adding a treatment factor • PRE-TEST POST-TEST REMOVING THE TREATMENT O 1 X O 2 _ X O 3 X 04
Experimental Designs Research design with more power to control for time • Pre-test post-test O 1 O 2 O 3 X O 4 O 5 O 6 • Pre-test post-test with control group O 1 O 2 O 3 X O 4 O 5 O 6
Did you bring your lab coat? • Considering true experiments are close to impossible or unethical in political science, we need to apply science differently. • Hence, this is why we in political science often use Quasi-experimental or nonexperimental research designs
Quasi-Experimental • Quasi-experiments: The researcher does not have control over the experiment, rather the experiment occurs in a “natural” setting. • Quasi-experimental design are typical in economics, sociology, public administration, urban planning, political sciences, etc.
Quasi-Experimental • A prominent example of this type of research is arguably by Samuel Huntington, who argues that Latin American immigration, especially Mexican, is altering US culture for the worse. • He essentially predicts that the United States will be a divided, less productive, society, ruining the past culture that has made the United States great. http: //www. foreignpolicy. com/story/cms. php? story_id=2495
Quasi-Experimental Huntington points out the following X variables: • Proximity of Mexico, Latin America to USA • Former ties to Mexico • Magnitude of recent wave of immigration • Duration of recent wave of immigration • Illegality He does this by observing what is going on today. It is crucial that one understands his assumptions and evaluates what he claims as evidence for his theory