Exam 2 - 01:43 ResearchDesignandtheLogicofControl...

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01:43 Research Design and the Logic of Control In this chapter you will learn: 1. The importance of rival explanations in political research 2. How experimental studies rule out rival causes 3. How observational studies control for rival causes 4. Three possible scenarios for the relationship between an independent variable and a  dependent variable, controlling for a rival cause. Test Group : composed of subjects who receive a treatment that the researcher believes is  causally linked to the dependent variable. Control Group : composed of subjects who do not receive the treatment that the researcher  believes is causally linked to the dependent variable. Rival explanation : an alternative cause for different values of the dependent value. Ex: you’re doing a study on the survival rate of a surgery, the control group is older less  healthy patients, while the test group is younger healthier patients. It could be these  differences that explain the better rates of survival and not the actual surgery itself. For every explanation we propose, and for every hypothesis we test, there are alternative causes  (rival explanations) that undermine our ability to evaluate the effect of the independent variable on  the dependent variable. Research Design : a set of procedures for evaluating the effect of an independent variable on a  dependent variable. Experimental study : ensures that the test group and the control group are the same in every  way, except for the independent variable. Observational study : allows the researcher to make controlled comparisons—observe the effect  of the independent variable on the dependent variable while being constant with all other factors  of the dependent variable. Most common approaches in political science. EXPERIMENTAL STUDIES Premeasurement stage : the investigator manipulates the test and control group so that both  groups are identical in the beginning. Treatment/intervention stage : the test group gets some treatment while the control group does  not.
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Postmeasurement stage : the dependent variable is measured again for both groups, to  measure any observed differences. Laboratory experiment : the control group and test group are brought outside of their normal  surroundings and studied in an environment built for the experiment. Field experiment : the control and test groups are studied in their normal surroundings and often  don’t know they are being studied. Random assignment
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This note was uploaded on 04/21/2011 for the course PLS 201 taught by Professor Ostrom during the Spring '08 term at Michigan State University.

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Exam 2 - 01:43 ResearchDesignandtheLogicofControl...

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