Download presentation
Presentation is loading. Please wait.
1
Political Science 30: Political Inquiry
Isolating Causal Factors Using Tables and Graphs Political Science 30: Political Inquiry
2
Isolating Causal Factors
Using Tables to “Hold Constant” a Confounding Variable Income and voting Education as a confound Using Graphs to “Hold Constant” A Confound or Another Causal Factor California Connected charts
3
Using Tables to “Hold Constant” a Confounding Variable
We want to test the hypothesis that “Americans who have higher incomes are more likely to vote.” IV: Level of Income DV: Likelihood of Voting Income Likelihood of Voting
4
Using Tables to “Hold Constant” a Confounding Variable
Wolfinger and Rosenstone present evidence of the bivariate correlation between income and voting.
5
Using Tables to “Hold Constant” a Confounding Variable
But wait! Education is a possible confounding variable because (Lecture #2): Education changes the likelihood of voting Education is correlated with income Education is causally prior to income Education Voting Income
6
Using Tables to “Hold Constant” a Confounding Variable
Thought Experiment: What if we could compare the voting behavior of two people who had the same level of education but different incomes? Me vs. my friends who went to law school This analysis “holds constant” education It isolates the effect of income on voting Same logic as experiments, natural experiments, and quasi-experiments
7
Using Tables to “Hold Constant” a Confounding Variable
Wolfinger and Rosenstone hold education constant by using a two-way table.
8
Using Tables to “Hold Constant” a Confounding Variable
Once they held education constant, they found that “rock bottom poverty seems to depress turnout somewhat. Beyond that, income does not have much effect on turnout. (p. 26)” Holding constant (or “controlling for”) a confound or another causal factor often teaches us about the bivariate correlation.
9
Using Graphs A scatterplot is one way to tell if two interval or ratio variables are correlated.
10
You can connect points with lines in a scatterplot
11
Using Graphs Line graphs tell us about trends over time, but watch the scale!
12
Using Graphs
13
Line Graphs Can Show Difference in Proportions
14
Using Graphs Bar graphs are helpful when your independent variable is nominal
15
Using Graphs to “Hold Constant” A Confound or Another Causal Factor
I wanted to see whether the presence of term limits (IV #1) made California’s Legislature less likely to alter the Gov’s budget (DV). Term Limits % altered Divided/Unified Government (IV #2)
16
Using Graphs to “Hold Constant” A Confound or Another Causal Factor
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.