Lecture 3: Comparing Alternative Explanations

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Lecture 3 Comparing Alternative Explanations
1. What Are Theories And Hypotheses? 2. What Is
Correlation? 3. Does Correlation Prove
Causation? 4. What Is Operationalization? 5.
Does Case Selection Matter? 6. What Is
Falsifiability? 7. What Are Necessary And
Sufficient Conditions? 8. Repair The Damage Or
Toss The Theory?
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What Is A Theory?
Derive
Deterministic Law
Empirical Analysis
Test
Probabilistic Tendency
Few Grand Theories in Political Science Mostly
Middle Range Theories
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What Is A Hypothesis?

• Simple Causal Explanations For Event Or Outcome
• An If-then Statement If X, Then Y.
• Dependent And Independent Variables
• Direction Of Causation (Positive Or Negative)

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Variables And Hypotheses
INDEPENDENT VARIABLE
DIRECTION OF RELATIONSHIP
DEPENDENT VARIABLE
X DEMOCRACY OLD CARS INDIVIDUALISM XENOPHOBIA
RISING INCOMES HETEROGENEITY
---------------(-)------------gt ---------------
(-)------------gt ---------------()------------gt
---------------()------------gt ---------------(
)------------gt ---------------()------------gt ---
------------()------------gt
Y WAR INVOLVEMENT BREAKDOWN SUICIDE ANTI-IMMI
GRATION LAWS COLOGNE PURCHASES FAILURE OF
DEMOCRACY
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Multiple Causes and Competing Explanations
Bipolarity
()
Shared Alliance
(-)
Joint Democracy
(-)
()
Military Weakness
()
Homogeneous Decision Making Bodies
()
Ideological Leaders
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What Is Correlation?

• Measure of the Linear Association Between Two
  Variables
• Direction of Relationship If X Rises, What
  Happens to Y?
• -- Positive Correlation
• -- Negative Correlation
• Strength of Relationship Strong Versus Weak
• -- Varies From -1.0 to 1.0

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Correlation
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(1)
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(2)
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r 0.75
r -0.75
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(3)
(4)
r - 1.0
r 0.0
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(5)
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r 0.0
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Is Correlation Enough?
1. Correlation Is Not Enough -- Spurious
Correlation 2. Popsicle Sales And Murders
Democracy And Battle Deaths 3. Process Tracing
Establishing A Case For Causation Task A
Examine Implicit Links In General Hypotheses X
---------------------------gt Y
A ---gt B ----gt C Task B Examine
Related Implications If X Causes Y, Then
Logically We Should Expect To Find That A
Causes B, C Results In D, ..
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What Is Operationalization?
1. Variable Versus A Constant 2. Example 1
Income A) Continuous Variable B) Categorical
Variable C) Dummy Or Dichotomous Variable 3.
Why Is Operationalization Important A)
Replication B) Validity C) Author Is
Explicit 3. Example 2 Democracy 4.
Definitions Matter
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Does Case Selection Matter?
1. Choosing Events To Study (e.g., Revolutions,
Elections, Coups, ) 2. Political Scientists
Want To Generalize Across Cases 3. Methods For
Choosing Cases A) Biased Selection -- Picking
Cases Which Support Your Theory B) Random
Selection -- Picking A Subset Of Cases From A
Population C) Critical Case -- Picking A Case
With The Deck Stacked For Or Against It 4. Why
Does More Matter? The Coin Tossing Example 5. Is
More Always Better? Confronting Trade-offs
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What Is Falsifiability?
1. All Hypotheses Should Be State In Falsifiable
Terms (i.e., You Can Think Of Evidence Which
Would Refute) 2. Example Democratic
Institutions --(-)--gt War Initiation 3. A
Non-falsifiable Theory Some Versions Of
Structural Marxism 4. Key Point Develop
Critical Thinking Skills -- Always Think About
What Would Falsify A Hypothesis
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Necessary Versus Sufficient Conditions
1. Traditional Ways Of Measuring The Relative
Importance Of Independent Variables 2.
Necessary Condition The Independent Variable
Must Be Present For The Outcome To Occur 3.
Sufficient Condition Any Time The Independent
Variable Is Present, The Outcome Occurs
Both Necessary And Sufficient
Neither Necessary Nor Sufficient
Necessary Condition
Sufficient Condition
X
Y
X
Y
X
Y
X
Y
X
Y
Y
Y
X
X
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Repairing The DamageOr Tossing The Theory?
1. What If Some Cases Do Not Support The
Theory? -- Purist Response The Theory Is
Falsified 2. But Most Theories In Social
Sciences Are Probabilistic 3. Failure May Be
Systematic Certain Cases May Fail -- Restrict
Theory To This Subset Of Cases 4. Some Theories
Are Clearly Wrong And Should Be Tossed -- But
Dont Toss The Baby Out With The Bath Water