Is there a relationship between factionalization of a country and the time in between elections?
Factiona lizatio n
laining length of coalition governments
POLS 3800 Introduction to Methods of Political Research
Dr. Judd Thornton
Office: 1013 Langdale Hall
Office Hours: M-F 9:3010:30
Goal of course
The goal is to introduce students to the methods used by political scientists to try
Why do we want a probabilistic model?
= $ + & +
Goals: hypothesize relationship; use sample to estimate model; assess usefulness of model
Sum of squared errors: +),& )*
Multiple Regression: Interaction Terms
Some relationships are conditional.
The relationship between X and Y depends on Z .
The impact the slope depends on the value of Z .
Quality = 0 + 1 Experience + 2 Female + 3 (Exp.
Multiple Regression: Dummy Variables
Categorical Independent Variables
What if were interested in the impact of gender?
Or race or ethnicity?
Income = + 1 Gender
Views Toward Hillary Clinton
Does gender matter?
Hillary = 0 + 1 Income
Move to model building.
Still testing a hypothesis.
y = mx + b
Linear, deterministic model.
Deterministic: y can always be found if we know x.
Social world is not deterministic.
y = + x + Random Error
We believe that education affects political participation. We
Participationi = 0 + 1 Educationi + ui
1 is the impact of education on participation.
We cannot establish a causal relationship.
We can rule ou
More on Omitted Variable Bias
If we exclude z,
1 = 1 + shared variance with z
We over or underestimate the impact of x on y .
We call this bias.
Hypothetical Example 1
Imagine the following is the true process:
Score on testi =
A reminder of what were doing:
We hypothesize a model:
= + 1 xi + ui
where 1 is the impact of x on y.
Were interested in explaining the part of the world thats
We want to find generalizable feature
Why use a dummy variable?
How do we code dummy variables?
Zero and one.
The impact of Maymester, seven-week summer courses, or
Fall/Spring on retention?
Two dummy variables.
k 1 dummy variables (where k i
The Big Picture
Lets Avoid being Casual about Causality
Goal is to explain systematic portion of the social world.
Avoid (exclusively) relying on anecdotes.
Does presentation of news influence attitudes?
We could study this experimentally!