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Research Design:

Research Design:. Alan Monroe: Chapter 3. The Concept of Causality (31). The types of research designs reviewed here are all intended to test whether one variable causes another or causes variation in another. Three (3) Requirements of Causality (31-32).

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Research Design:

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  1. Research Design: Alan Monroe: Chapter 3

  2. The Concept of Causality (31) • The types of research designs reviewed here are all intended to test whether one variable causes another or causesvariation in another.

  3. Three (3) Requirements of Causality (31-32) Correlation: two things tend to occur at the same time (not sufficient to est. causation) • Examples: • Whenever there is a foreign policy crisis, presidential • popularity increases. • If Catholic, then more likely to oppose abortion. Time Order: cause has to happen before the effect. Non-Spuriousness: to make sure any correlation we observe between the independent and dependent variables is not caused by other factors.

  4. Types of Research Designs (32) • 1. True Experimental Design • It involves a group of subjects (units of analysis), which is divided into two groups (randomly, to assure they are identical on the DV). • Experimental and Control Groups • The first group is the experimental group, the second is the control group. The experimental group receives a stimulus (the Independent Variable), the control does not. • Post-Test • A Post-Testis then given to both groups to test the effect (DV) of the stimulus (IV). You then comparethe results. • …

  5. True Experimental Design

  6. Examples of Experimental Design(33) • Introduction to American Government Example: Does it Increase Political Interest? (see Chart on p. 33) • Hypothesis: taking course increases political interest in • college students. • …

  7. Problems With True Experimental Design • Hard to get truly Representative Samples (hard to get accurate • sample of an entire population, one solution is to reduce size of • population: college students for example.) • Artificial setting (does it test real behavior) • Outside Influences (you can never fully isolate subjects from • other variables.) • Ethical Considerations (cannot mistreat or expose humans to • harmful stimuli) • …

  8. The Quasi Experimental (Natural Experiment) (37) • 2) Quasi Experimental It is also called the before and after test: you compare the DV (a Pretest and Posttest) before and after the IV has been applied. • Differs from Experimental Design in several ways: • Groups are not assigned (we observe some happen, and then go back and sort into experimental and control groups.) • Requires a Pretest of DV so amount of change can be measured. • …

  9. Quasi Experimental Design

  10. Quasi Experimental: Presidential Debate Example (38) • Hypothesis: watching a presidential debate increases intensity of support for the candidate. • Subjects: students in a class • Pretest: before debate give them a survey measuring their attitudes about the candidates • Posttest: did they watch the debate, and what is the strength of • their preference.

  11. Meeting Conditions of Causality: Quasi Experimental (38) • Correlation: change between pretest and post-test has to be • significant (indicating IV had an effect) • Time Order: includes measure of DV before and after IV. • Non-Spurious: effect of all outside forces is theoretically equal • on all subjects. (they are all exposed to same amount of TV ads, thus any changes comes from the IV). • …

  12. Correlational Design (40) • It is very simple: collecting data on the IV and DV in order to see if there is a pattern or relationship. It is the most common design in political science. • Examples: • Turnout in Urban Areas • IV: urbanization • DV: voter turnout • Operational Definitions: • Urbanization: percentage of pop. Living in “urban places,” • according to US Census. • Turnout: votes cast divided by voting-age population.

  13. Correlational Design

  14. Meeting Conditions of Causality: Correlational Design (38) • Correlation: is directly tested between the IV and DV. • Time Order: it is weakest here: there is no consideration for the point in time when the IV and DV occurred. Have to reliable on IV that are known to exist before DV, like race, gender. • Non-Spurious: considers control variables. • …

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