1 Introduction Overview of the Book How to Use this Book Introduction to R 10

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1 List of Tables List of Figures Preface xiii xv xvii 1 Introduction Overview of the Book How to Use this Book Introduction to R Arithmetic Operations Objects Vectors Functions Data Files Saving Objects Packages Programming and Learning Tips Summary Exercises Bias in Self-Reported Turnout Understanding World Population Dynamics 29 2 Causality Racial Discrimination in the Labor Market Subsetting the Data in R Logical Values and Operators Relational Operators Subsetting Simple Conditional Statements Factor Variables Causal Effects and the Counterfactual 46

2 viii Copyright, Princeton University Press. No part of this book may be 2.4 Randomized Controlled Trials The Role of Randomization Social Pressure and Voter Turnout Observational Studies Minimum Wage and Unemployment Confounding Bias Before-and-After and Difference-in-Differences Designs Descriptive Statistics for a Single Variable Quantiles Standard Deviation Summary Exercises Efficacy of Small Class Size in Early Education Changing Minds on Gay Marriage Success of Leader Assassination as a Natural Experiment 73 3 Measurement Measuring Civilian Victimization during Wartime Handling Missing Data in R Visualizing the Univariate Distribution Bar Plot Histogram Box Plot Printing and Saving Graphs Survey Sampling The Role of Randomization Nonresponse and Other Sources of Bias Measuring Political Polarization Summarizing Bivariate Relationships Scatter Plot Correlation Quantile Quantile Plot Clustering Matrix in R List in R The k-means Algorithm Summary Exercises Changing Minds on Gay Marriage: Revisited Political Efficacy in China and Mexico Voting in the United Nations General Assembly Prediction Predicting Election Outcomes Loops in R 124

3 ix General Conditional Statements in R Poll Predictions Linear Regression Facial Appearance and Election Outcomes Correlation and Scatter Plots Least Squares Regression towards the Mean Merging Data Sets in R Model Fit Regression and Causation Randomized Experiments Regression with Multiple Predictors Heterogenous Treatment Effects Regression Discontinuity Design Summary Exercises Prediction Based on Betting Markets Election and Conditional Cash Transfer Program in Mexico Government Transfer and Poverty Reduction in Brazil Discovery Textual Data The Disputed Authorship of The Federalist Papers Document-Term Matrix Topic Discovery Authorship Prediction Cross Validation Network Data Marriage Network in Renaissance Florence Undirected Graph and Centrality Measures Twitter-Following Network Directed Graph and Centrality Spatial Data The 1854 Cholera Outbreak in London Spatial Data in R Colors in R US Presidential Elections Expansion of Walmart Animation in R Summary Exercises Analyzing the Preambles of Constitutions International Trade Network Mapping US Presidential Election Results over Time 239

4 x Copyright, Princeton University Press. No part of this book may be 6 Probability Probability Frequentist versus Bayesian Definition and Axioms Permutations Sampling with and without Replacement Combinations Conditional Probability Conditional, Marginal, and Joint Probabilities Independence Bayes Rule Predicting Race Using Surname and Residence Location Random Variables and Probability Distributions Random Variables Bernoulli and Uniform Distributions Binomial Distribution Normal Distribution Expectation and Variance Predicting Election Outcomes with Uncertainty Large Sample Theorems The Law of Large Numbers The Central Limit Theorem Summary Exercises The Mathematics of Enigma A Probability Model for Betting Market Election Prediction Election Fraud in Russia Uncertainty Estimation Unbiasedness and Consistency Standard Error Confidence Intervals Margin of Error and Sample Size Calculation in Polls Analysis of Randomized Controlled Trials Analysis Based on Student s t-distribution Hypothesis Testing Tea-Tasting Experiment The General Framework One-Sample Tests Two-Sample Tests Pitfalls of Hypothesis Testing Power Analysis Linear Regression Model with Uncertainty Linear Regression as a Generative Model Unbiasedness of Estimated Coefficients 375

5 xi Standard Errors of Estimated Coefficients Inference about Coefficients Inference about Predictions Summary Exercises Sex Ratio and the Price of Agricultural Crops in China File Drawer and Publication Bias in Academic Research The 1932 German Election in the Weimar Republic Next 397 General Index 401 R Index 406