PS102Lecture19

PS102Lecture19 - Cross-Tabulations & Scatter Plots...

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Political Science 102 Introduction to Political Inquiry Lecture 19 Cross-Tabulations & Scatter Plots
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Investigating Bivariate Relationships Central goal of political science is to discover generalizable causal relationships between political variables Statistics provide tools for evaluating relationships between variables Also provide tools for assessing causal impact NO test of causality is definitive We can use statistical methods to try to approximate experimental conditions
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Statistical Tools for Measuring Relationships Cross-tabulations and scatter plots Most basic evaluation tools Flexible and allow researcher to see patterns in the data Measures of Association Provide quantitative measures of strength and direction of relationship Problems with generalizability Regression Analysis Most flexible tool for examining multivariate relationships Many tools and variants to address questions of causality
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Patterns of Relationships Between Variables General Association (positive or negative) Monotonic Linear Curvilinear Association (positive and negative) Convex Concave Contingent Association Interactive / Conditional Conditions may change presence or nature of relationship
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Strength and Fit of Relationships Strength and fit are SEPARATE concepts Strength = increase or decrease in Y that is associated with a change in X Fit = precision with which X can predict Y Both A & B are strong relationships
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Cross-Tabulations Also known as contingency tables, cross- classification tables, and bivariate frequency distributions Most useful for categorical or ordinal data Difficult to observe patterns with many cells Can group interval or ratio data for cross- tabs One variable is displayed in columns and the second in rows Easy to see non-linear patterns Easier to see patterns by reporting cell percentages (in rows or columns)
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Priority of Health Care -> tabulation of q1_health_care by gender Rank of | priority - | Health | Gender care | Male Female | Total -----------+----------------------+---------- 1 | 217 351 | 568 2 | 439 633 | 1,072 3 | 264 307 |
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This note was uploaded on 10/21/2011 for the course POL SCI 102 taught by Professor Gelpi during the Spring '11 term at Duke.

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PS102Lecture19 - Cross-Tabulations & Scatter Plots...

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