CONTENTS 1 Introduction ... 1 1.1 The Nature of the Subjects ... 1 1.2 The Plan of This Book ... 4 Appendix ... 5 Functions and Graphs ... 5 Elasticity ... 7 Problems ... 9 PART Ⅰ Data and Description ... 11 2 Economic Data ... 13 2.1 General Considerations ... 13 2.2 Cross-Section Data ... 16 Errors in Data ... 22 2.3 Time-Series Data ... 23 Change and Growth ... 26 Constructed Variables ... 27 2.4 Plotting a Time-Series Variable ... 29 Appendix ... 33 Logarithms ... 33 Logarithmic Transformations ... 37 Problems ... 40 3 Descriptive Statistics ... 43 3.1 Univariate Statistics ... 43 Measures of Central Tendency ... 43 Measures of Dispersion ... 45 Computation ... 48 3.2 Linear Transformations ... 50 3.3 Bivariate Statistics ... 53 Appendix: Summations ... 57 Problems ... 59 4 Frequency Distributions ... 62 4.1 Discrete Data Variables ... 62 4.2 Continuous Data Variables ... 66 Proportions ... 69 Problems ... 74 PART Ⅱ Specification and Estimation of Regression Models ... 77 5 Simple Regression: Theory ... 79 5.1 Specification of the Model ... 79 5.2 Estimation of the Model ... 82 5.3 Interpretation of the Regression ... 86 5.4 Measures of Fit ... 89 The Standard Error of the Regression, SER ... 90 The Coefficient of Deterinination, R² ... 91 5.5 The Effects of Linear Transformation ... 94 5.6 Regression Through the Origin ... 98 Appendix ... 100 Derivation of the OLS Estimators ... 100 Equivalence of R² and (r)² ... 101 Problems ... 102 6 Simple Regression: Application ... 105 6.1 Interpretation of the Coefficients ... 105 6.2 The Earnings Function and the Consumption Function ... 108 The Earnings Function ... 108 The Consumption Function ... 110 6.3 Alternative Model Specifications ... 111 Ratios of Variables ... 111 Differences of Variables ... 112 Lagged Variables and First Differences ... 113 6.4 The Reciprocal Specification ... 115 6.5 Logarithmic Functional Forms ... 118 The Log-Linear Specification ... 118 The Semilog Specification ... 122 Appendix: The Coefficients in Logarithmic Models ... 126 Problems ... 129 7 Multiple Regression: Theory and Application ... 132 7.1 Two Explanatory Variables ... 132 The Earnings Function ... 136 7.2 The General Case ... 138 Comparing Regressions ... 140 The Consumption Function ... 142 7.3 Dummy Variables ... 143 More Than Two Categories ... 148 7.4 Polynomial Specifications ... 151 7.5 Logarithmic Specifications ... 155 The Demand for Money ... 155 The Earnings Function ... 156 7.6 Specification Questions ... 157 The Causal Nexus ... 157 Consequences of Misspecification ... 159 Multicollinearity ... 161 Problems ... 163 PART Ⅲ Probability Distributions ... 167 8 Probability Theory ... 169 8.1 Outcomes and Probabilities ... 169 8.2 Events ... 171 8.3 Unions and Intersections ... 172 8.4 Conditional Probability and Independence ... 174 8.5 A Pair of Dice ... 177 Problems ... 179 9 Random Variables and Probability Distributions ... 182 9.1 Discrete Random Variables ... 182 Mean and Standard Deviation ... 186 9.2 Random Variables and Samples of Data ... 187 9.3 The Binomial Distribution ... 189 9.4 Continuous Random Variables ... 192 9.5 Transformations ... 199 Appendix ... 201 Joint Probability Distributions ... 201 Linear Combinations ... 204 Problems ... 206 10 The Normal and t Distributions ... 209 10.1 The Normal Distribution ... 209 The Standard Normal ... 209 Other Normal Distributions ... 213 10.2 The t Distribution ... 218 Appendix ... 221 The Chi-Square Distribution ... 221 The F Distribution ... 223 Problems ... 224 PART Ⅳ Inference in Regression ... 227 11 Sampling Theory in Regression ... 229 11.1 The Normal Regression Model ... 229 11.2 An Experiment in Sampling ... 233 11.3 The Sampling Distributions: Theory ... 236 Probability Calculations ... 238 11.4 The Sampling Distributions: Application ... 240 Probability Calculations ... 242 11.5 Interval Estimation ... 243 11.6 A Compendium of Reported Regressions ... 247 Appendix ... 250 Derivation of a Sampling Distribution ... 250 Derivation of the Confidence Interval ... 252 Problems ... 253 12 Hypothesis Testing ... 256 12.1 Specification of Hypotheses ... 256 12.2 The Basic Significance Test ... 257 The Underlying Logic ... 258 Reformulation ... 261 Practical Application ... 262 12.3 The Test for Sign ... 267 12.4 Tests for Specific Coefficient Values ... 272 Hypothesis Testing and Confidence Intervals ... 274 12.5 P-Values ... 276 Problems ... 280 13 Estimation and Regression Problems ... 282 13.1 Confidence Intervals for Prediction ... 282 13.2 Comparing Alternative Estimators ... 285 13.3 Multicollinearity ... 288 13.4 Misspecification ... 290 Specification Strategy ... 294 13.5 Sample Selection ... 294 Appendix: Expectations ... 297 Problems ... 300 PART Ⅴ Topics in Econometrics ... 303 14 F Tests and Dummy Variable Outcomes ... 305 14.1 F Tests in Multiple Regression ... 305 Theory ... 307 Applications ... 309 The Chow Test ... 312 14.2 Models for Dummy Variable Outcomes ... 316 Linear Probability Model ... 317 Probit and Logit Models ... 318 Problems ... 323 15 Heteroscedasticity and Autocorrelation ... 325 15.1 Heteroscedasticity ... 325 The Model and Its Consequences ... 326 Detection ... 328 Estimation ... 331 15.2 Autocorrelation ... 332 The Model ... 333 Consequences of Autocorrelation for OLS ... 337 Testing for Autocorrelation ... 337 Estimation Procedures ... 340 Problems ... 343 16 Regression and Time Series ... 345 16.1 Distributed Lags ... 345 The General Distributed Lag ... 346 The Koyck Model ... 348 Partial Adjustment and Adaptive Expectations ... 351 Estimation Problems ... 352 The Almon Lag Model and Other Lag Specifications ... 353 16.2 Trends and Seasonality ... 357 Trends ... 357 Seasonality ... 359 16.3 Random Walks and Spurious Regressions ... 361 Problems ... 363 17 Simultaneous-Equation Models ... 365 17.1 The Nature of the Models ... 365 The Reduced Form ... 368 Estimation and Simulation ... 371 17.2 Estimation ... 373 Two-Stage Least Squares ... 373 17.3 Identification ... 375 The Order Condition ... 376 Interpretation ... 378 Problems ... 379 PART Ⅵ Topics in Statistics ... 381 18 Inference for the Mean and Variance ... 383 18.1 The Sampling Distribution of X ‾ ... 383 18.2 Inference Regarding μx ... 388 Hypothesis Tests ... 389 Interval Estimates ... 391 18.3 The Sampling Distribution of S²x ... 392 18.4 Inference Regarding σ²x ... 392 Problems ... 394 19 Chi-Square Tests and Analysis of Variance ... 396 19.1 Chi-Square Tests ... 396 Test of Goodness of Fit ... 397 Test of Independence ... 399 19.2 Analysis of Variance and Regression ... 400 ANOVA Table for Regression ... 400 One-Way ANOVA ... 402 Two-Way ANOVA ... 404 Problems ... 405 Statistical Tables ... 407 Answers to Selected Problems ... 421 Bibliography ... 437 Index ... 441