Political Science 30:Political Inquiry

Qualitative Research Design II

Selecting on the Dependent VariableMills’ Method of AgreementMills’ Method of Difference

ExamplesClem MillerDreze and Sen

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.”

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 can’t cause the dependent var.

This method can only disprove a hypothesis, because it can’t find a correlation.

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.

Case Early Industrialization?

Viable Socialist Party?

France No Yes

Britain Yes Yes

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.

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.

Case Early Indust.? Feudalism? Viable Social Party?

France No Yes Yes

Britain Yes Yes Yes

USA Yes No No

Example: Clem Miller

This Congressman writing home to his supporters tells the story of two different lobbying efforts on behalf of farmers.

Let’s 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.

Example: Clem Miller

Case Economic Trouble?

Sympathy of Officials?

Well Organized?

Govt. Help?

Walnut

Growers

Poultry Men

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)”

Comparing Many Research Methods: Measurement Validity

Measurement validity judges the gap between your conceptual definition and your operational definition.Qualitative – Highest measurement validityThe measurement validity of other research

methods (Lab experiments, quasi/natural experiments, and quantitative research) really depends on what you are trying to measure.

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 – highestQuasi/Natural experiments – mediumQualitative research – mediumQuantitative research – lowest

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 – highestQuasi/Natural experiments – mediumLab experiments – lowQualitative research – low

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.