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Political Science 30: Political Inquiry

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Comparing Many Research Methods: Measurement Validity ... Comparing Many Research Methods: Internal Validity ... Comparing Many Research Methods: External Validity ... – PowerPoint PPT presentation

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Title: Political Science 30: Political Inquiry


1
Political Science 30Political Inquiry
2
Qualitative Research Design II
  • Selecting on the Dependent Variable
  • Mills Method of Agreement
  • Mills Method of Difference
  • Examples
  • Clem Miller
  • Dreze and Sen

3
Selecting on the Dependent Variable
  • Selecting cases according to the value of the
    dependent variable that they take on is more
    controversial than selecting on the independent
    variable.
  • It allows you to look at extreme values or
    divergent cases.
  • However, if this design is to lead to meaningful
    causal inferences, it is crucial to select
    observations without regard to values of the
    explanatory variables. K.K.V.

4
Selecting on the Dependent Variable Method of
Agreement
  • When you use Mills Method of Agreement, you
    select cases that take on the same values of the
    dependent variable.
  • This helps you to rule out possible causes,
    because independent variables that vary over
    these cases cant cause the dependent var.
  • This method can only disprove a hypothesis,
    because it cant find a correlation.

5
Selecting on the Dependent Variable Method of
Agreement
  • This design could help us rule out early
    industrialization as a cause of whether a
    country has a viable socialist party.

6
Selecting on the Dependent Variable Method of
Difference
  • When you use Mills Method of Difference, you
    select cases that take on different values of the
    dependent variable.
  • After you have selected your cases, you determine
    what values they take on for some independent
    variables.
  • Perhaps one independent variable will vary across
    your cases, and explain the D.V.

7
Selecting on the Dependent Variable Method of
Difference
  • Adding a country that has no viable socialist
    party can add causal leverage to our early
    investigation.

8
Example Clem Miller
  • This Congressman writing home to his supporters
    tells the story of two different lobbying efforts
    on behalf of farmers.
  • Lets assume that his process of case selection
    came in the same order that his narrative is
    written.
  • If so, he selected on independent variables and
    used the Most Similar Systems design.

9
Example Clem Miller
10
Example Dreze and Sen
  • Both countries began a new political regime at
    mid-century with large populations and little
    wealth.
  • They have diverged since then There is little
    doubt that as far a morbidity, mortality, and
    longevity are concerned, China has a large and
    decisive lead over India. (p. 205)
  • What has brought about that lead is a matter of
    very considerable interest. (p. 206)

11
Comparing Many Research Methods Measurement
Validity
  • Measurement validity judges the gap between your
    conceptual definition and your operational
    definition.
  • Qualitative Highest measurement validity
  • The measurement validity of other research
    methods (Lab experiments, quasi/natural
    experiments, and quantitative research) really
    depends on what you are trying to measure.

12
Comparing Many Research Methods Internal Validity
  • Internal validity judges how well a research
    design has tested a causal relationship, in the
    cases examined. Random assignment is the key.
  • Lab Experiments highest
  • Quasi/Natural experiments medium
  • Qualitative research medium
  • Quantitative research lowest

13
Comparing Many Research Methods External Validity
  • External validity is how confident we can be that
    a causal relationship identified in our cases can
    be generalized to the outside world. Random
    sampling is key
  • Quantitative research highest
  • Quasi/Natural experiments medium
  • Lab experiments low
  • Qualitative research low

14
Comparing Many Research Methods Overall Lessons
  • The best research design depends on your research
    question and the particular problems that it
    poses.
  • The best research uses a mixture of methods to
    test a hypothesis.
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