Figures and Tables

Preface

Introduction: Getting Started with Stata

I.1 Datasets for Stata Companion

I.2 A Quick Tour of Stata

I.3 Running Commands in Stata

I.4 Quick Access to Tutorials and Resources

Chapter 1 Using Stata for Data Analysis

1.1 General Syntax of Stata Commands

1.2 Using Stata’s Graphic User Interface Effectively

1.3 Do-files

1.4 Printing Results and Copying Output

1.5 Customizing Your Display

1.6 Log Files

1.7 Getting Help

Chapter 1 Exercises

Chapter 2 Descriptive Statistics

2.1 Identifying Levels of Measurement

2.2 Describing Nominal Variables

A Closer Look: Weighted and Unweighted Analysis: What’s the Difference?

2.3 Describing Ordinal Variables

2.4 Bar Charts for Nominal and Ordinal Variables

2.5 Describing Interval Variables

A Closer Look: Stata’s Graphics Editor

2.6 Histograms for Interval Variables

2.7 Obtaining Case-Level Information

Chapter 2 Exercises

Chapter 3 Transforming Variables

3.1 Creating Dummy Variables

3.2 Applying Math Operators to Variables

3.3 Managing Variable Descriptions and Labels

3.4 Collapsing Variables into Simplified Categories

3.5 Centering or Standardizing a Numeric Variable

3.6 Creating an Additive Index

Chapter 3 Exercises

Chapter 4 Making Comparisons

4.1 Cross-Tabulation Analysis

A Closer Look: The replace Command

4.2 Mean Comparison Analysis

A Closer Look: The format Command

4.3 Making Comparisons with Interval-Level Independent Variables

Chapter 4 Exercises

Chapter 5 Graphing Relationships and Describing Patterns

5.1 Graphs for Binary Dependent Variables

5.1.1 Simple Bar Charts with Nominal-Level Independent Variables

5.1.2 Area Chart with Ordinal-Level Independent Variables

5.1.3 Graphs with Interval-Level Independent Variables

5.2 Graphs for Nominal-Level Dependent Variables

5.2.1 Clustered Bar Charts with Nominal-Level Independent Variables

5.2.2 Multiple Line Plots with Ordinal-Level Independent Variables

5.2.3 Graphs with Interval-Level Independent Variables

5.3 Graphs for Ordinal-Level Dependent Variables

5.3.1 Using Bars to Represent Select Values

5.3.2 Stacked Bar Chart for Ordinal-Ordinal Relationship

5.3.3 Graphs with Interval-Level Independent Variables

5.4 Graphs for Interval-Level Dependent Variables

5.4.1 Plotting Means with Bars or Lines

Chapter 5 Exercises

Chapter 6 Random Assignment and Sampling

6.1 Random Assignment

6.1.1 Two Groups with Equal Probability

6.1.2 Multiple Groups with Varying Probabilities

6.1.3 Random Assignment to Predetermined-Size Groups

6.2 Analyzing the Results of an Experiment

6.2.1 Assessing Random Assignment

6.2.2 Evaluating the Effect of Treatment

6.3 Random Sampling

6.3.1 Simple Random Sampling with Replacement

6.3.2 Simple Random Sampling without Replacement

6.3.3 Systematic Random Samples

6.3.4 Clustered and Stratified Random Samples

6.4 Selecting Cases for Qualitative Analysis

6.4.1 Most Similar Systems

6.4.2 Most Different Systems

6.5 Analyzing Data Ethically

6.5.1 Ethical Issues in Data Analysis

6.5.2 Ten Tips for Writing Replication Code

Chapter 6 Exercises

Chapter 7 Making Controlled Comparisons

7.1 Cross-Tabulation Analysis with a Control Variable

7.1.1 Start with a Basic Cross-Tabulation

7.1.2 Controlling for Another Variable

7.1.3 Interpreting Controlled Cross-Tabulations

A Closer Look: The If Qualifier

7.2 Visualizing Controlled Comparisons with Categorical Dependent Variables

7.3 Mean Comparison Analysis with a Control Variable

7.3.1 Start with Basic Mean Comparison Table

7.3.2 Adding Control Variables

7.3.3 Interpreting a Controlled Mean Comparison

7.4 Visualizing Controlled Mean Comparisons

Chapter 7 Exercises

Chapter 8 Foundations of Inference

8.1 Estimating Population Parameters with Simulations

8.2 Expected Shape of Sampling Distributions

8.2.1 Central Limit Theorem and the Normal Distribution

8.2.2 Normal Distribution of Sample Proportions

8.2.3 Normal Distribution of Sample Means

8.2.4 The Standard Normal Distribution

8.2.5 The Empirical Rule (68-95-99 Rule)

8.3 Confidence Interval and Margins of Error

8.3.1 Critical Values for Confidence Intervals

8.3.2 Reporting the Confidence Interval for a Sample Proportions

8.3.2 Reporting the Confidence Interval for a Sample Means

8.4 Student’s t-Distribution: When You’re Not Completely Normal

8.4.1 The t-Distribution’s Role in Inferential Statistics

8.4.1 Critical Values of t-Distributions

Chapter 8 Exercises

Chapter 9 Hypothesis Tests with One and Two Samples

9.1 Role of the Null Hypothesis

9.2 Testing Hypotheses with Sample Proportions

9.2.1 Testing One Sample Proportion Against Hypothesized Value

9.2.2 Testing Difference Between Two Sample Proportions Using Groups

9.2.3 Testing Difference Between Two Sample Proportions Using Variables

9.2.4 Testing Hypotheses about Proportions with Weighted Data

9.3 Testing Hypotheses with Sample Means

9.3.1 Testing One Sample Mean Against Hypothesized Value

9.3.2 Testing the Difference Between Two Sample Means Using Groups

9.3.3 Testing the Difference Between Two Sample Means Using Variables

9.3.4 T-Test Variations from Assumptions about Variance

9.3.5 Testing Hypotheses about Means with Weighted Data

Chapter 9 Exercises

Chapter 10 Chi-Square Test and Analysis of Variance

10.1 The Chi-Square Test of Independence

10.1.1 How the Chi-Square Test Works

10.1.2 Conducting a Chi-Square Test

10.1.3 Example with Nominal-Level Independent Variable

A Closer Look: Chi-Square Test with Weighted Data

10.1.4 Reporting and Interpreting Results

A Closer Look: Other Applications of Chi-Square Tests

10.2 Measuring the Strength of Association between Categorical Variables

10.3 Chi-Square Test and Measures of Association in Controlled Comparisons

10.3.1 Analyzing an Ordinal-Level Relationship with a Control Variable

10.3.2 Analyzing a Nominal-Level Relationship with a Control Variable (and Weighted Observations)

10.4 Analysis of Variance (ANOVA)

10.4.2 Single Factor ANOVA

10.4.4 Stata’s F-Distribution Functions

Chapter 10 Exercises

Chapter 11 Correlation and Bivariate Regression

11.1 Correlation Analysis

11.1.1 Correlation between Two Variables

11.1.2 Correlation Among More than Two Variables

A Closer Look: Other Types and Application of Correlation Analysis

11.2 Bivariate Regression Analysis

A Closer Look: Treating Census as a Sample

A Closer Look: R-Squared and Adjusted R-Squared: What’s the Difference?

11.3 Creating a Scatterplot with a Linear Prediction Line

A Closer Look: Creating Graphs with Multiple Layered Elements

A Closer Look: What If a Scatterplot Doesn’t Show a Linear Relationship?

11.4 Correlation and Bivariate Regression Analysis with Weighted Data

A Closer Look: Creating Tables of Regression Results

Chapter 11 Exercises

Chapter 12 Multiple Regression

12.1 Multiple Regression Analysis

12.1.1 Estimating and Interpreting a Multiple Regression Model

12.1.2 Visualizing Multiple Regression with Bubble Plots

12.1.3 Multiple Regression with Weighted Observations

12.2 Regression with Multiple Dummy Variables

12.2.1 Estimating and Interpreting Regression with Multiple Dummy Variables

12.2.2 Changing the Reference Category

12.2.3 Visualizing Regression with Multiple Dummy Variables

12.3 Interaction Effects in Multiple Regression

12.3.1 Estimating Regression Model with Interaction Term

12.3.2 Graphing Linear Prediction Lines for Interaction Relationships

Chapter 12 Exercises

Chapter 13 Analyzing Regression Residuals

13.1 Expected Values, Observed Values, and Regression Residuals

13.1.1 Example from Bivariate Regression Analysis

13.1.2 Residuals from Multiple Regression Analysis

13.2 Squared and Standarized Residuals

13.2.2 Standardized Residuals

13.3 Assumptions about Regression Residuals

13.4 Analyzing Graphs of Regression Residuals

13.4.1 Histogram of Regression Residuals

13.4.2 Residual Diagnostic Plots

13.5 Testing Regression Assumptions with Residuals

13.5.1 Testing Assumption that Residuals are Normally Distributed

13.5.2 Testing the Constant Variance Assumption

15.3.3 Regression Diagnostics for Multiple Regression Analysis

A Closer Look: Other Regression Diagnostic Tests

13.6 What If You Diagnose Problems with Residuals?

Chapter 13 Exercises

Chapter 14 Logistic Regression

14.1 Odds, Logged Odds, and Probabilities

14.2 Estimating Logistic Regression Models

14.2.1 Logistic Regression with One Independent Variable

14.2.2 Reporting and Interpreting Odds Ratios

14.2.3 Evaluating Model Fit

A Closer Look: Logistic Regression Analysis with Weighted Observations

14.3 Logistic Regression with Multiple Independent Variables

14.4 Graphing Predicted Probabilities with One Independent Variable

14.4.1 Interval-Level Independent Variable

14.4.2 Categorical Independent Variable

A Closer Look: Marginal Effects and Expected Changes in Probability

14.5 Graphing Predicted Probabilities with Multiple Independent Variables

14.5.1 One Categorical and One Interval-Level Independent Variable

14.5.2 Two Categorical Independent Variables

A Closer Look: Stata’s Quiet Mode

14.5.3 Plotting Predicted Probabilities with atmeans Option

14.5.4 Combining atmeans and over Options

Chapter 14 Exercises

Chapter 15 Doing Your Own Political Analysis

15.1 Doable Research Ideas

15.1.1 Political Knowledge and Interest

15.1.2 Self-Interest and Policy Preferences

15.1.3 Economic Performance and Election Outcomes

15.1.4 Electoral Turnout in Comparative Perspective

15.1.5 Correlates of State Policies

15.1.6 Religion and Politics

15.2 Getting Data into Stata

15.2.1 Opening Stata Formatted Datasets

15.2.2 Importing Microsoft Excel Datasets

15.2.3 Using HTML Table Data

15.2.4 Entering Data with Stata’s Data Editor

15.3 Writing It Up

15.3.1 The Research Question

15.3.3 Data, Hypotheses, and Analysis

15.3.4 Conclusions and Implications

Chapter 15 Exercises

Appendix

Table A-1: Variables in the Debate Dataset in Alphabetical Order

Table A-2: Variables in the GSS Dataset in Alphabetical Order

Table A-3: Variables in the NES Dataset in Alphabetical Order

Table A-4: Variables in the States Dataset by Topic

Table A-5: Variables in the World Dataset by Topic