伍德里奇计量经济学英文版各章总结

CHAPTER 1

TEACHING NOTES

You have substantial latitude about what to emphasize in Chapter 1. I find it useful to talk about the economics of crime example (Example 1.1) and the wage example (Example 1.2) so that students see, at the outset, that econometrics is linked to economic reasoning, even if the economics is not complicated theory.

I like to familiarize students with the important data structures that empirical economists use, focusing primarily on cross-sectional and time series data sets, as these are what I cover in a first-semester course. It is probably a good idea to mention the growing importance of data sets that have both a cross-sectional and time dimension.

I spend almost an entire lecture talking about the problems inherent in drawing causal inferences in the social sciences. I do this mostly through the agricultural yield, return to education, and crime examples. These examples also contrast experimental and nonexperimental (observational) data. Students studying business and finance tend to find the term structure of interest rates example more relevant, although the issue there is testing the implication of a simple theory, as opposed to inferring causality. I have found that spending time talking about these examples, in place of a formal review of probability and statistics, is more successful (and more enjoyable for the students and me).

CHAPTER 2

TEACHING NOTES

This is the chapter where I expect students to follow most, if not all, of the algebraic derivations. In class I like to derive at least the unbiasedness of the OLS slope coefficient, and usually I derive the variance. At a minimum, I talk about the factors affecting the variance. To simplify the notation, after I emphasize the assumptions in the population model, and assume random sampling, I just condition on the values of the explanatory variables in the sample. Technically, this is justified by random sampling because, for example, E(u i|x1,x2,…,x n) = E(u i|x i) by independent sampling. I find that students are able to focus on the key assumption SLR.4 and subsequently take my word about how conditioning on the independent variables in the sample is harmless. (If you prefer, the appendix to Chapter 3 does the conditioning argument carefully.) Because statistical inference is no more difficult in multiple regression than in simple regression, I postpone inference until Chapter 4. (This reduces redundancy and allows you to focus on the interpretive differences between simple and multiple regression.)

You might notice how, compared with most other texts, I use relatively few assumptions to derive the unbiasedness of the OLS slope estimator, followed by the formula for its variance. This is because I do not introduce redundant or unnecessary assumptions. For example, once SLR.4 is assumed, nothing further about the relationship between u and x is needed to obtain the unbiasedness of OLS under random sampling.

CHAPTER 3

TEACHING NOTES

For undergraduates, I do not work through most of the derivations in this chapter, at least not in detail. Rather, I focus on interpreting the assumptions, which mostly concern the population. Other than random sampling, the only assumption that involves more than population considerations is the assumption about no perfect collinearity, where the possibility of perfect collinearity in the sample (even if it does not occur in the population) should be touched on. The more important issue is perfect collinearity in the population, but this is fairly easy to dispense with via examples. These come from my experiences with the kinds of model specification issues that beginners have trouble with.

The comparison of simple and multiple regression estimates – based on the particular sample at hand, as opposed to their statistical properties – usually makes a strong impression. Sometimes I do not bother with the “partialling out” interpretation of multiple regression.

As far as statistical properties, notice how I treat the problem of including an irrelevant variable: no separate derivation is needed, as the result follows form Theorem 3.1.

I do like to derive the omitted variable bias in the simple case. This is not much more difficult than showing unbiasedness of OLS in the simple regression case under the first four Gauss-Markov assumptions. It is important to get the students thinking about this problem early on, and before too many additional (unnecessary) assumptions have been introduced.

I have intentionally kept the discussion of multicollinearity to a minimum. This partly indicates my bias, but it also reflects reality. It is, of course, very important for students to understand the potential consequences of having highly correlated independent variables. But this is often beyond our control, except that we can ask less of our multiple regression analysis. If two or more explanatory variables are highly correlated in the sample, we should not expect to precisely estimate their ceteris paribus effects in the population.

I find extensive treatments of multicollinearity, where one “tests” or somehow “solves” the multicollinearity problem, to be misleading, at best. Even the organization of some texts gives the impression that imperfect multicollinearity is somehow a violation of the Gauss-Markov assumptions: they include multicollinearity in a chapter or part of the book devoted to “violation of the basic assumptions,” or something like that. I have noticed that master’s students who have had some undergraduate econometrics are often confused on the multicollinearity issue. It is very important that students not confuse multicollinearity among the included explanatory variables in a regression model with the bias caused by omitting an important variable.

I do not prove the Gauss-Markov theorem. Instead, I emphasize its implications. Sometimes, and certainly for advanced beginners, I put a special case of Problem 3.12 on a midterm exam, where I make a particular choice for the function g(x). Rather than have the students directly compare the variances, they should

appeal to the Gauss-Markov theorem for the superiority of OLS over any other linear, unbiased estimator.

CHAPTER 4

TEACHING NOTES

At the start of this chapter is good time to remind students that a specific error distribution played no role in the results of Chapter 3. That is because only the first two moments were derived under the full set of Gauss-Markov assumptions. Nevertheless, normality is needed to obtain exact normal sampling distributions (conditional on the explanatory variables). I emphasize that the full set of CLM assumptions are used in this chapter, but that in Chapter 5 we relax the normality assumption and still perform approximately valid inference. One could argue that the classical linear model results could be skipped entirely, and that only large-sample analysis is needed. But, from a practical perspective, students still need to know where the t distribution comes from because virtually all regression packages report t statistics and obtain p -values off of the t distribution. I then find it very easy to

cover Chapter 5 quickly, by just saying we can drop normality and still use t statistics and the associated p -values as being approximately valid. Besides, occasionally students will have to analyze smaller data sets, especially if they do their own small surveys for a term project.

It is crucial to emphasize that we test hypotheses about unknown population

parameters. I tell my students that they will be punished if they write something like

H 0:1

? = 0 on an exam or, even worse, H 0: .632 = 0. One useful feature of Chapter 4 is its illustration of how to rewrite a population model so that it contains the parameter of interest in testing a single restriction. I find this is easier, both theoretically and practically, than computing variances that can, in some cases, depend on numerous covariance terms. The example of testing equality of the return to two- and four-year colleges illustrates the basic method, and shows that the respecified model can have a useful interpretation. Of course, some statistical packages now provide a standard error for linear combinations of estimates with a simple command, and that should be taught, too.

One can use an F test for single linear restrictions on multiple parameters, but this is less transparent than a t test and does not immediately produce the standard error needed for a confidence interval or for testing a one-sided alternative. The trick of rewriting the population model is useful in several instances, including obtaining confidence intervals for predictions in Chapter 6, as well as for obtaining confidence intervals for marginal effects in models with interactions (also in Chapter

6).

The major league baseball player salary example illustrates the difference

between individual and joint significance when explanatory variables (rbisyr and hrunsyr in this case) are highly correlated. I tend to emphasize the R -squared form of the F statistic because, in practice, it is applicable a large percentage of the time, and it is much more readily computed. I do regret that this example is biased toward students in countries where baseball is played. Still, it is one of the better examples

of multicollinearity that I have come across, and students of all backgrounds seem to get the point.

CHAPTER 5

TEACHING NOTES

Chapter 5 is short, but it is conceptually more difficult than the earlier chapters, primarily because it requires some knowledge of asymptotic properties of estimators. In class, I give a brief, heuristic description of consistency and asymptotic normality before stating the consistency and asymptotic normality of OLS. (Conveniently, the same assumptions that work for finite sample analysis work for asymptotic analysis.) More advanced students can follow the proof of consistency of the slope coefficient in the bivariate regression case. Section E.4 contains a full matrix treatment of asymptotic analysis appropriate for a master’s level course.

An explicit illustration of what happens to standard errors as the sample size grows emphasizes the importance of having a larger sample. I do not usually cover the LM statistic in a first-semester course, and I only briefly mention the asymptotic efficiency result. Without full use of matrix algebra combined with limit theorems for vectors and matrices, it is very difficult to prove asymptotic efficiency of OLS.

I think the conclusions of this chapter are important for students to know, even though they may not fully grasp the details. On exams I usually include true-false type questions, with explanation, to test the students’ understanding of asymptotics. [For example: “In large samples we do not have to worry about omitted variable bias.” (False). Or “Even if the error term is not normally distributed, in large samples we can still compute approximately valid confidence intervals under the Gauss-Markov assumptions.” (True).]

CHAPTER6

TEACHING NOTES

I cover most of Chapter 6, but not all of the material in great detail. I use the example in Table 6.1 to quickly run through the effects of data scaling on the important OLS statistics. (Students should already have a feel for the effects of data scaling on the coefficients, fitting values, and R-squared because it is covered in Chapter 2.) At most, I briefly mention beta coefficients; if students have a need for them, they can read this subsection.

The functional form material is important, and I spend some time on more complicated models involving logarithms, quadratics, and interactions. An important point for models with quadratics, and especially interactions, is that we need to evaluate the partial effect at interesting values of the explanatory variables. Often, zero is not an interesting value for an explanatory variable and is well outside the range in the sample. Using the methods from Chapter 4, it is easy to obtain confidence intervals for the effects at interesting x values.

As far as goodness-of-fit, I only introduce the adjusted R-squared, as I think using a slew of goodness-of-fit measures to choose a model can be confusing to novices (and does not reflect empirical practice). It is important to discuss how, if we fixate on a high R-squared, we may wind up with a model that has no interesting ceteris paribus interpretation.

I often have students and colleagues ask if there is a simple way to predict y when log(y) has been used as the dependent variable, and to obtain a goodness-of-fit measure for the log(y) model that can be compared with the usual R-squared obtained when y is the dependent variable. The methods described in Section 6.4 are easy to implement and, unlike other approaches, do not require normality.

The section on prediction and residual analysis contains several important topics, including constructing prediction intervals. It is useful to see how much wider the prediction intervals are than the confidence interval for the conditional mean. I usually discuss some of the residual-analysis examples, as they have real-world applicability.

CHAPTER 7

TEACHING NOTES

This is a fairly standard chapter on using qualitative information in regression analysis, although I try to emphasize examples with policy relevance (and only cross-sectional applications are included.).

In allowing for different slopes, it is important, as in Chapter 6, to appropriately interpret the parameters and to decide whether they are of direct interest. For example, in the wage equation where the return to education is allowed to depend on gender, the coefficient on the female dummy variable is the wage differential between women and men at zero years of education. It is not surprising that we cannot estimate this very well, nor should we want to. In this particular example we would drop the interaction term because it is insignificant, but the issue of interpreting the parameters can arise in models where the interaction term is significant.

In discussing the Chow test, I think it is important to discuss testing for differences in slope coefficients after allowing for an intercept difference. In many applications, a significant Chow statistic simply indicates intercept differences. (See the example in Section 7.4 on student-athlete GPAs in the text.) From a practical perspective, it is important to know whether the partial effects differ across groups or whether a constant differential is sufficient.

I admit that an unconventional feature of this chapter is its introduction of the linear probability model. I cover the LPM here for several reasons. First, the LPM is being used more and more because it is easier to interpret than probit or logit models. Plus, once the proper parameter scalings are done for probit and logit, the estimated effects are often similar to the LPM partial effects near the mean or median values of the explanatory variables. The theoretical drawbacks of the LPM are often of secondary importance in practice. Computer Exercise C7.9 is a good one to illustrate that, even with over 9,000 observations, the LPM can deliver fitted values strictly between zero and one for all observations.

If the LPM is not covered, many students will never know about using econometrics to explain qualitative outcomes. This would be especially unfortunate for students who might need to read an article where an LPM is used, or who might want to estimate an LPM for a term paper or senior thesis. Once they are introduced to purpose and interpretation of the LPM, along with its shortcomings, they can tackle nonlinear models on their own or in a subsequent course.

A useful modification of the LPM estimated in equation (7.29) is to drop kidsge6 (because it is not significant) and then define two dummy variables, one for kidslt6 equal to one and the other for kidslt6 at least two. These can be included in place of kidslt6 (with no young children being the base group). This allows a diminishing marginal effect in an LPM. I was a bit surprised when a diminishing effect did not materialize.

CHAPTER 8

TEACHING NOTES

This is a good place to remind students that homoskedasticity played no role in showing that OLS is unbiased for the parameters in the regression equation. In addition, you probably should mention that there is nothing wrong with the R-squared or adjusted R-squared as goodness-of-fit measures. The key is that these are estimates of the population R-squared, 1 – [Var(u)/Var(y)], where the variances are the unconditional variances in the population. The usual R-squared, and the adjusted version, consistently estimate the population R-squared whether or not Var(u|x) = Var(y|x) depends on x. Of course, heteroskedasticity causes the usual standard errors, t statistics, and F statistics to be invalid, even in large samples, with or without normality.

By explicitly stating the homoskedasticity assumption as conditional on the explanatory variables that appear in the conditional mean, it is clear that only heteroskedasticity that depends on the explanatory variables in the model affects the validity of standard errors and test statistics. The version of the Breusch-Pagan test in the text, and the White test, are ideally suited for detecting forms of heteroskedasticity that invalidate inference obtained under homoskedasticity. If heteroskedasticity depends on an exogenous variable that does not also appear in the mean equation, this can be exploited in weighted least squares for efficiency, but only rarely is such a variable available. One case where such a variable is available is when an individual-level equation has been aggregated. I discuss this case in the text but I rarely have time to teach it.

As I mention in the text, other traditional tests for heteroskedasticity, such as the Park and Glejser tests, do not directly test what we want, or add too many assumptions under the null. The Goldfeld-Quandt test only works when there is a natural way to order the data based on one independent variable. This is rare in practice, especially for cross-sectional applications.

Some argue that weighted least squares estimation is a relic, and is no longer necessary given the availability of heteroskedasticity-robust standard errors and test statistics. While I am sympathetic to this argument, it presumes that we do not care much about efficiency. Even in large samples, the OLS estimates may not be precise

enough to learn much about the population parameters. With substantial heteroskedasticity we might do better with weighted least squares, even if the weighting function is misspecified. As discussed in the text on pages 288-289, one can, and probably should, compute robust standard errors after weighted least squares. For asymptotic efficiency comparisons, these would be directly comparable to the heteroskedasiticity-robust standard errors for OLS.

Weighted least squares estimation of the LPM is a nice example of feasible GLS, at least when all fitted values are in the unit interval. Interestingly, in the LPM examples in the text and the LPM computer exercises, the heteroskedasticity-robust standard errors often differ by only small amounts from the usual standard errors. However, in a couple of cases the differences are notable, as in Computer Exercise

C8.7.

CHAPTER 9

TEACHING NOTES

The coverage of RESET in this chapter recognizes that it is a test for neglected nonlinearities, and it should not be expected to be more than that. (Formally, it can be shown that if an omitted variable has a conditional mean that is linear in the included explanatory variables, RESET has no ability to detect the omitted variable. Interested readers may consult my chapter in Companion to Theoretical Econometrics, 2001, edited by Badi Baltagi.) I just teach students the F statistic version of the test.

The Davidson-MacKinnon test can be useful for detecting functional form misspecification, especially when one has in mind a specific alternative, nonnested model. It has the advantage of always being a one degree of freedom test.

I think the proxy variable material is important, but the main points can be made with Examples 9.3 and 9.4. The first shows that controlling for IQ can substantially change the estimated return to education, and the omitted ability bias is in the expected direction. Interestingly, education and ability do not appear to have an interactive effect. Example 9.4 is a nice example of how controlling for a previous value of the dependent variable – something that is often possible with survey and nonsurvey data – can greatly affect a policy conclusion. Computer Exercise 9.3 is also a good illustration of this method.

I rarely get to teach the measurement error material, although the attenuation bias result for classical errors-in-variables is worth mentioning.

The result on exogenous sample selection is easy to discuss, with more details given in Chapter 17. The effects of outliers can be illustrated using the examples. I think the infant mortality example, Example 9.10, is useful for illustrating how a single influential observation can have a large effect on the OLS estimates.

With the growing importance of least absolute deviations, it makes sense to at least discuss the merits of LAD, at least in more advanced courses. Computer Exercise 9.9 is a good example to show how mean and median effects can be very different, even though there may not be “outliers” in the usual sense.

CHAPTER 10

TEACHING NOTES

Because of its realism and its care in stating assumptions, this chapter puts a somewhat heavier burden on the instructor and student than traditional treatments of time series regression. Nevertheless, I think it is worth it. It is important that students learn that there are potential pitfalls inherent in using regression with time series data that are not present for cross-sectional applications. Trends, seasonality, and high persistence are ubiquitous in time series data. By this time, students should have a firm grasp of multiple regression mechanics and inference, and so you can focus on those features that make time series applications different from

cross-sectional ones.

I think it is useful to discuss static and finite distributed lag models at the same time, as these at least have a shot at satisfying the Gauss-Markov assumptions.

Many interesting examples have distributed lag dynamics. In discussing the time series versions of the CLM assumptions, I rely mostly on intuition. The notion of strict exogeneity is easy to discuss in terms of feedback. It is also pretty apparent that, in many applications, there are likely to be some explanatory variables that are not strictly exogenous. What the student should know is that, to conclude that OLS is unbiased – as opposed to consistent – we need to assume a very strong form of exogeneity of the regressors. Chapter 11 shows that only contemporaneous exogeneity is needed for consistency.

Although the text is careful in stating the assumptions, in class, after discussing strict exogeneity, I leave the conditioning on X implicit, especially when I discuss the no serial correlation assumption. As this is a new assumption I spend some time on it. (I also discuss why we did not need it for random sampling.)

Once the unbiasedness of OLS, the Gauss-Markov theorem, and the sampling distributions under the classical linear model assumptions have been covered – which can be done rather quickly – I focus on applications. Fortunately, the students already know about logarithms and dummy variables. I treat index numbers in this chapter because they arise in many time series examples.

A novel feature of the text is the discussion of how to compute goodness-of-fit measures with a trending or seasonal dependent variable. While detrending or deseasonalizing y is hardly perfect (and does not work with integrated processes), it is better than simply reporting the very high R-squareds that often come with time series regressions with trending variables.

CHAPTER 11

TEACHING NOTES

Much of the material in this chapter is usually postponed, or not covered at all, in an introductory course. However, as Chapter 10 indicates, the set of time series applications that satisfy all of the classical linear model assumptions might be very small. In my experience, spurious time series regressions are the hallmark of many

student projects that use time series data. Therefore, students need to be alerted to the dangers of using highly persistent processes in time series regression equations. (Spurious regression problem and the notion of cointegration are covered in detail in Chapter 18.)

It is fairly easy to heuristically describe the difference between a weakly dependent process and an integrated process. Using the MA(1) and the stable AR(1) examples is usually sufficient.

When the data are weakly dependent and the explanatory variables are contemporaneously exogenous, OLS is consistent. This result has many applications, including the stable AR(1) regression model. When we add the appropriate homoskedasticity and no serial correlation assumptions, the usual test statistics are asymptotically valid.

The random walk process is a good example of a unit root (highly persistent) process. In a one-semester course, the issue comes down to whether or not to first difference the data before specifying the linear model. While unit root tests are covered in Chapter 18, just computing the first-order autocorrelation is often sufficient, perhaps after detrending. The examples in Section 11.3 illustrate how different first-difference results can be from estimating equations in levels.

Section 11.4 is novel in an introductory text, and simply points out that, if a model is dynamically complete in a well-defined sense, it should not have serial correlation. Therefore, we need not worry about serial correlation when, say, we test the efficient market hypothesis. Section 11.5 further investigates the homoskedasticity assumption, and, in a time series context, emphasizes that what is contained in the explanatory variables determines what kind of heteroskedasticity is ruled out by the usual OLS inference. These two sections could be skipped without loss of continuity.

CHAPTER 12

TEACHING NOTES

Most of this chapter deals with serial correlation, but it also explicitly considers heteroskedasticity in time series regressions. The first section allows a review of what assumptions were needed to obtain both finite sample and asymptotic results. Just as with heteroskedasticity, serial correlation itself does not invalidate R-squared. In fact, if the data are stationary and weakly dependent, R-squared and adjusted

R-squared consistently estimate the population R-squared (which is well-defined under stationarity).

Equation (12.4) is useful for explaining why the usual OLS standard errors are not generally valid with AR(1) serial correlation. It also provides a good starting point for discussing serial correlation-robust standard errors in Section 12.5. The subsection on serial correlation with lagged dependent variables is included to debunk the myth that OLS is always inconsistent with lagged dependent variables and serial correlation. I do not teach it to undergraduates, but I do to master’s student s.

Section 12.2 is somewhat untraditional in that it begins with an asymptotic t test for AR(1) serial correlation (under strict exogeneity of the regressors). It may seem heretical not to give the Durbin-Watson statistic its usual prominence, but I do believe the DW test is less useful than the t test. With nonstrictly exogenous regressors I cover only the regression form of Durbin’s test, as the h statistic is asymptotically equivalent and not always computable.

Section 12.3, on GLS and FGLS estimation, is fairly standard, although I try to show how comparing OLS estimates and FGLS estimates is not so straightforward. Unfortunately, at the beginning level (and even beyond), it is difficult to choose a course of action when they are very different.

I do not usually cover Section 12.5 in a first-semester course, but, because some econometrics packages routinely compute fully robust standard errors, students can be pointed to Section 12.5 if they need to learn something about what the corrections do.

I do cover Section 12.5 for a master’s level course in applied econometrics (after the first-semester course).

I also do not cover Section 12.6 in class; again, this is more to serve as a reference for more advanced students, particularly those with interests in finance. One important point is that ARCH is heteroskedasticity and not serial correlation, something that is confusing in many texts. If a model contains no serial correlation, the usual heteroskedasticity-robust statistics are valid. I have a brief subsection on correcting for a known form of heteroskedasticity and AR(1) errors in models with strictly exogenous regressors.

CHAPTER 13

TEACHING NOTES

While this chapter falls under “Advanced Topics,” most of this chapter requires no more sophistication than the previous chapters. (In fact, I would argue that, with the possible exception of Section 13.5, this material is easier than some of the time series chapters.)

Pooling two or more independent cross sections is a straightforward extension of cross-sectional methods. Nothing new needs to be done in stating assumptions, except possibly mentioning that random sampling in each time period is sufficient. The practically important issue is allowing for different intercepts, and possibly different slopes, across time.

The natural experiment material and extensions of the difference-in-differences estimator is widely applicable and, with the aid of the examples, easy to understand.

Two years of panel data are often available, in which case differencing across time is a simple way of removing g unobserved heterogeneity. If you have covered Chapter 9, you might compare this with a regression in levels using the second year of data, but where a lagged dependent variable is included. (The second approach only requires collecting information on the dependent variable in a previous year.) These often give similar answers. Two years of panel data, collected before and after a policy change, can be very powerful for policy analysis.

Having more than two periods of panel data causes slight complications in that the errors in the differenced equation may be serially correlated. (However, the traditional assumption that the errors in the original equation are serially uncorrelated is not always a good one. In other words, it is not always more appropriate to used fixed effects, as in Chapter 14, than first differencing.) With large N and relatively small T, a simple way to account for possible serial correlation after differencing is to compute standard errors that are robust to arbitrary serial correlation and hetero-skedasticity. Econometrics packages that do cluster analysis (such as Stata) often allow this by specifying each cross-sectional unit as its own cluster.

CHAPTER 14

TEACHING NOTES

My preference is to view the fixed and random effects methods of estimation as applying to the same underlying unobserved effects model. The name “unobserved effect” is neutral to the issue of whether the time-constant effects should be treated as fixed parameters or random variables. With large N and relatively small T, it almost always makes sense to treat them as random variables, since we can just view the unobserved a i as being drawn from the population along with the observed variables. Especially for undergraduates and master’s students, it seems sensible to not raise the philosophical issues underlying the professional debate. In my mind, the key issue in most applications is whether the unobserved effect is correlated with the observed explanatory variables. The fixed effects transformation eliminates the unobserved effect entirely whereas the random effects transformation accounts for the serial correlation in the composite error via GLS. (Alternatively, the random effects transformation only eliminates a fraction of the unobserved effect.)

As a practical matter, the fixed effects and random effects estimates are closer when T is large or when the variance of the unobserved effect is large relative to the variance of the idiosyncratic error. I think Example 14.4 is representative of what often happens in applications that apply pooled OLS, random effects, and fixed effects, at least on the estimates of the marriage and union wage premiums. The random effects estimates are below pooled OLS and the fixed effects estimates are below the random effects estimates.

Choosing between the fixed effects transformation and first differencing is harder, although useful evidence can be obtained by testing for serial correlation in the first-difference estimation. If the AR(1) coefficient is significant and negative (say, less than .3, to pick a not quite arbitrary value), perhaps fixed effects is preferred.

Matched pairs samples have been profitably used in recent economic applications, and differencing or random effects methods can be applied. In an equation such as (14.12), there is probably no need to allow a different intercept for each sister provided that the labeling of sisters is random. The different intercepts might be needed if a certain feature of a sister that is not included in the observed controls is used to determine the ordering. A statistically significant intercept in the differenced equation would be evidence of this.

TEACHING NOTES

When I wrote the first edition, I took the novel approach of introducing instrumental variables as a way of solving the omitted variable (or unobserved heterogeneity) problem. Traditionally, a student’s first exposure to IV methods comes by way of simultaneous equations models. Occasionally, IV is first seen as a method to solve the measurement error problem. I have even seen texts where the first appearance of IV methods is to obtain a consistent estimator in an AR(1) model with AR(1) serial correlation.

The omitted variable problem is conceptually much easier than simultaneity, and stating the conditions needed for an IV to be valid in an omitted variable context is straightforward. Besides, most modern applications of IV have more of an unobserved heterogeneity motivation. A leading example is estimating the return to education when unobserved ability is in the error term. We are not thinking that education and wages are jointly determined; for the vast majority of people, education is completed before we begin collecting information on wages or salaries. Similarly, in studying the effects of attending a certain type of school on student performance, the choice of school is made and then we observe performance on a test. Again, we are primarily concerned with unobserved factors that affect performance and may be correlated with school choice; it is not an issue of simultaneity.

The asymptotics underlying the simple IV estimator are no more difficult than for the OLS estimator in the bivariate regression model. Certainly consistency can be derived in class. It is also easy to demonstrate how, even just in terms of inconsistency, IV can be worse than OLS if the IV is not completely exogenous.

At a minimum, it is important to always estimate the reduced form equation and test whether the IV is partially correlated with endogenous explanatory variable.

The material on multicollinearity and 2SLS estimation is a direct extension of the OLS case. Using equation (15.43), it is easy to explain why multicollinearity is generally more of a problem with 2SLS estimation.

Another conceptually straightforward application of IV is to solve the measurement error problem, although, because it requires two measures, it can be hard to implement in practice.

Testing for endogeneity and testing any overidentification restrictions is something that should be covered in second semester courses. The tests are fairly easy to motivate and are very easy to implement.

While I provide a treatment for time series applications in Section 15.7, I admit to having trouble finding compelling time series applications. These are likely to be found at a less aggregated level, where exogenous IVs have a chance of existing. (See also Chapter 16.)

TEACHING NOTES

I spend some time in Section 16.1 trying to distinguish between good and inappropriate uses of SEMs. Naturally, this is partly determined by my taste, and many applications fall into a gray area. But students who are going to learn about SEMS should know that just because two (or more) variables are jointly determined does not mean that it is appropriate to specify and estimate an SEM. I have seen many bad applications of SEMs where no equation in the system can stand on its own with an interesting ceteris paribus interpretation. In most cases, the researcher either wanted to estimate a tradeoff between two variables, controlling for other factors – in which case OLS is appropriate – or should have been estimating what is (often pejora tively) called the “reduced form.”

The identification of a two-equation SEM in Section 16.3 is fairly standard except that I emphasize that identification is a feature of the population. (The early work on SEMs also had this emphasis.) Given the treatment of 2SLS in Chapter 15, the rank condition is easy to state (and test).

Romer’s (1993) inflation and openness example is a nice example of using aggregate cross-sectional data. Purists may not like the labor supply example, but it has become common to view labor supply as being a two-tier decision. While there are different ways to model the two tiers, specifying a standard labor supply function conditional on working is not outside the realm of reasonable models.

Section 16.5 begins by expressing doubts of the usefulness of SEMs for aggregate models such as those that are specified based on standard macroeconomic models. Such models raise all kinds of thorny issues; these are ignored in virtually all texts, where such models are still used to illustrate SEM applications.

SEMs with panel data, which are covered in Section 16.6, are not covered in any other introductory text. Presumably, if you are teaching this material, it is to more advanced students in a second semester, perhaps even in a more applied course. Once students have seen first differencing or the within transformation, along with IV methods, they will find specifying and estimating models of the sort contained in Example 16.8 straightforward. Levitt’s example concernin g prison populations is especially convincing because his instruments seem to be truly exogenous.

CHAPTER 17

TEACHING NOTES

I emphasize to the students that, first and foremost, the reason we use the probit and logit models is to obtain more reasonable functional forms for the response probability. Once we move to a nonlinear model with a fully specified conditional distribution, it makes sense to use the efficient estimation procedure, maximum likelihood. It is important to spend some time on interpreting probit and logit estimates. In particular, the students should know the rules-of-thumb for comparing probit, logit, and LPM estimates. Beginners sometimes mistakenly think that,

because the probit and especially the logit estimates are much larger than the LPM estimates, the explanatory variables now have larger estimated effects on the response probabilities than in the LPM case. This may or may not be true.

I view the Tobit model, when properly applied, as improving functional form for corner solution outcomes. In most cases it is wrong to view a Tobit application as a data-censoring problem (unless there is true data censoring in collecting the data or because of institutional constraints). For example, in using survey data to estimate the demand for a new product, say a safer pesticide to be used in farming, some farmers will demand zero at the going price, while some will demand positive pounds per acre. There is no data censoring here; some farmers find it optimal to use none of the new pesticide. The Tobit model provides more realistic functional forms for E(y|x) and E(y|y > 0,x) than a linear model for y. With the Tobit model, students may be tempted to compare the Tobit estimates with those from the linear model and conclude that the Tobit estimates imply larger effects for the independent variables. But, as with probit and logit, the Tobit estimates must be scaled down to be comparable with OLS estimates in a linear model. [See Equation (17.27); for an example, see Computer Exercise C17.3.]

Poisson regression with an exponential conditional mean is used primarily to improve over a linear functional form for E(y|x). The parameters are easy to interpret as semi-elasticities or elasticities. If the Poisson distributional assumption is correct, we can use the Poisson distribution compute probabilities, too. But over-dispersion is often present in count regression models, and standard errors and likelihood ratio statistics should be adjusted to reflect this. Some reviewers of the first edition complained about either the inclusion of this material or its location within the chapter. I think applications of count data models are on the rise: in microeconometric fields such as criminology, health economics, and industrial organization, many interesting response variables come in the form of counts. One suggestion was that Poisson regression should not come between the Tobit model in Section 17.2 and Section 17.4, on censored and truncated regression. In fact, I put the Poisson regression model between these two topics on purpose: I hope it helps emphasize that the material in Section 17.2 is purely about functional form, as is Poisson regression. Sections 17.4 and 17.5 deal with underlying linear models, but where there is a data-observability problem.

Censored regression, truncated regression, and incidental truncation are used for missing data problems. Censored and truncated data sets usually result from sample design, as in duration analysis. Incidental truncation often arises from self-selection into a certain state, such as employment or participating in a training program. It is important to emphasize to students that the underlying models are classical linear models; if not for the missing data or sample selection problem, OLS would be the efficient estimation procedure.

CHAPTER 18

TEACHING NOTES

Several of the topics in this chapter, including testing for unit roots and cointegration, are now staples of applied time series analysis. Instructors who like their course to be more time series oriented might cover this chapter after Chapter 12, if time permits. Or, the chapter can be used as a reference for ambitious students who wish to be versed in recent time series developments.

The discussion of infinite distributed lag models, and in particular geometric

DL and rational DL models, gives one particular interpretation of dynamic regression models. But one must emphasize that only under fairly restrictive assumptions on the serial correlation in the error of the infinite DL model does the dynamic regression consistently estimate the parameters in the lag distribution. Computer Exercise

C18.1 provides a good illustration of how the GDL model, and a simple RDL model, can be too restrictive.

Example 18.5 tests for cointegration between the general fertility rate and the value of the personal exemption. There is not much evidence of cointegration, which sheds further doubt on the regressions in levels that were used in Chapter 10. The error correction model for holding yields in Example 18.7 is likely to be of interest to students in finance. As a class project, or a term project for a student, it would be interesting to update the data to see if the error correction model is stable over time.

The forecasting section is heavily oriented towards regression methods and, in particular, autoregressive models. These can be estimated using any econometrics package, and forecasts and mean absolute errors or root mean squared errors are easy to obtain. The interest rate data sets (for example, INTQRT.RAW) can be updated

to do much more recent out-of-sample forecasting exercises.

CHAPTER 19

TEACHING NOTES

This is a chapter that students should read if you have assigned them a term paper. I used to allow students to choose their own topics, but this is difficult in a first-semester course, and places a heavy burden on instructors or teaching assistants, or both. I now assign a common topic and provide a data set with about six weeks left in the term. The data set is cross-sectional (because I teach time series at the end of the course), and I provide guidelines of the kinds of questions students should try to answer. (For example, I might ask them to answer the following questions: Is there a marriage premium for NBA basketball players? If so, does it depend on race? Can the premium, if it exists, be explained by productivity differences?) The specifics are up to the students, and they are to craft a 10- to 15-page paper on their own. This gives them practice writing the results in a way that is easy-to-read, and forces them to interpret their findings. While leaving the topic to each student’s discretion is more interesting, I find that many students flounder with an open-ended assignment until it is too late. Naturally, for a second-semester course, or a senior seminar, students would be expected to design their own topic, collect their own data, and then write a more substantial term paper.

计量经济学实验报告英文版

Econometrics report Class number: No number: Eglish name: Chinese name:

Contents Background and Data Analysis 2-5 and model T-test 6-8 F-test 8-10 Summary,and,suggestion 11

BACKGROUND ●The report below is about the food sales , I instance the resident population (10 000 ) , per capita income the first year , meat sales , egg sales , the fish sales . ●In order to build mathematical models to understand the relationship of each variable and its food sales , and I take statistics of Tianjin from 1994 to 2007 the demand for food Among Y X1 X2 X3 X4 X5 1 98.4500 153.2000 560.2000 6.5300 1.2300 1.8900 2 100.7000 190.0000 603.1100 9.1200 1.3000 2.0300 3 102.8000 240.3000 668.0500 8.1000 1.8000 2.7100 4 133.9500 301.1200 715.4700 10.1000 2.0900 3.0000 5 140.1300 361.0000 724.2700 10.9300 2.3900 3.2900 6 143.1100 420.0000 736.1300 11.8500 3.9000 5.2400 7 146.1500 491.7760 748.9100 12.2800 5.1300 6.8300 8 144.6000 501.0000 760.3200 13.5000 5.4700 8.3600 9 146.9400 529.2000 774.9200 15.2900 6.0900 10.0700 10 158.5500 552.7200 785.3000 18.1000 7.9700 12.5700 11 169.6800 771.7600 795.5000 19.6100 10.1800 15.1200 12 162.1400 811.8000 804.8000 17.2200 11.7900 18.2500 13 170.0900 988.4300 814.9400 18.6000 11.5400 20.5900 14 178.6900 1094.6500 828.7300 23.5300 11.6800 23.3700

计量经济学 案例分析

第二章 案例分析 研究目的：分析各地区城镇居民计算机拥有量与城镇居民收入水平的关系，对更多规律的研究具有指导意义. 一． 模型设定 2011年年底城镇居民家庭平均每百户计算机拥有量Y 与城镇居民平均每人全年家庭总收入X 的关系 图2.1 各地区城镇居民每百户计算机拥有量与人均总收入的散点图 由图可知，各地区城镇居民每百户计算机拥有量随着人均总收入水平的提高而增加，近似于线性关系，为分析其数量性变动规律，可建立如下简单线性回归模型： Y t =β1+β2X t +u t 50 60 708090100 110120130140 X Y

二．估计参数 假定所建模型及其随机扰动项u i满足各项古典假设，用普通最小二乘法（OLSE）估计模型参数.其结果如下： 表2.1 回归结果 Dependent Variable: Y Method: Least Squares Date: 11/13/17 Time: 12:50 Sample: 1 31 Included observations: 31 Variable Coefficient Std. Error t-Statistic Prob. C 11.95802 5.622841 2.126686 0.0421 X 0.002873 0.000240 11.98264 0.0000 R-squared 0.831966 Mean dependent var 77.08161 Adjusted R-squared 0.826171 S.D. dependent var 19.25503 S.E. of regression 8.027957 Akaike info criterion 7.066078 Sum squared resid 1868.995 Schwarz criterion 7.158593 Log likelihood -107.5242 Hannan-Quinn criter. 7.096236 F-statistic 143.5836 Durbin-Watson stat 1.656123 Prob(F-statistic) 0.000000 由表2.1可得， β1=11.9580，β2=0.0029 故简单线性回归模型可写为： ^ Y X t t=11.9580+0.0029 其中：SE(β1)=5.6228, SE(β2)=0.0002 R-squared=0.8320，F=143.5836，n=31

计量经济学(伍德里奇第五版中文版)答案

第1章 解决问题的办法 1.1（一）理想的情况下，我们可以随机分配学生到不同尺寸的类。也就是说，每个学生被分配一个不同的类的大小，而不考虑任何学生的特点，能力和家庭背景。对于原因，我们将看到在第2章中，我们想的巨大变化，班级规模（主题，当然，伦理方面的考虑和资源约束）。 （二）呈负相关关系意味着，较大的一类大小是与较低的性能。因为班级规模较大的性能实际上伤害，我们可能会发现呈负相关。然而，随着观测数据，还有其他的原因，我们可能会发现负相关关系。例如，来自较富裕家庭的儿童可能更有可能参加班级规模较小的学校，和富裕的孩子一般在标准化考试中成绩更好。另一种可能性是，在学校，校长可能分配更好的学生，以小班授课。或者，有些家长可能会坚持他们的孩子都在较小的类，这些家长往往是更多地参与子女的教育。 （三）鉴于潜在的混杂因素- 其中一些是第（ii）上市- 寻找负相关关系不会是有力的证据，缩小班级规模，实际上带来更好的性能。在某种方式的混杂因素的控制是必要的，这是多元回归分析的主题。 1.2（一）这里是构成问题的一种方法：如果两家公司，说A和B，相同的在各方面比B公司à用品工作培训之一小时每名工人，坚定除外，多少会坚定的输出从B公司的不同？ （二）公司很可能取决于工人的特点选择在职培训。一些观察到的特点是多年的教育，多年的劳动力，在一个特定的工作经验。企业甚至可能歧视根据年龄，性别或种族。也许企业选择提供培训，工人或多或少能力，其中，“能力”可能是难以量化，但其中一个经理的相对能力不同的员工有一些想法。此外，不同种类的工人可能被吸引到企业，提供更多的就业培训，平均，这可能不是很明显，向雇主。 （iii）该金额的资金和技术工人也将影响输出。所以，两家公司具有完全相同的各类员工一般都会有不同的输出，如果他们使用不同数额的资金或技术。管理者的素质也有效果。 （iv）无，除非训练量是随机分配。许多因素上市部分（二）及（iii）可有助于寻找输出和培训的正相关关系，即使不在职培训提高工人的生产力。 1.3没有任何意义，提出这个问题的因果关系。经济学家会认为学生选择的混合学习和工作（和其他活动，如上课，休闲，睡觉）的基础上的理性行为，如效用最大化的约束，在一个星期只有168小时。然后我们可以使用统计方法来衡量之间的关联学习和工作，包括回归分析，我们覆盖第2章开始。但我们不会声称一个变量“使”等。他们都选择学生的变量。 第2章 解决问题的办法

计量经济学案例分析汇总

计量经济学案例分析1 一、研究的目的要求 居民消费在社会经济的持续发展中有着重要的作用。居民合理的消费模式和居民适度的消费规模有利于经济持续健康的增长，而且这也是人民生活水平的具体体现。改革开放以来随着中国经济的快速发展，人民生活水平不断提高，居民的消费水平也不断增长。但是在看到这个整体趋势的同时，还应看到全国各地区经济发展速度不同，居民消费水平也有明显差异。例如，2002年全国城市居民家庭平均每人每年消费支出为元, 最低的黑龙江省仅为人均元，最高的上海市达人均10464元，上海是黑龙江的倍。为了研究全国居民消费水平及其变动的原因，需要作具体的分析。影响各地区居民消费支出有明显差异的因素可能很多，例如，居民的收入水平、就业状况、零售物价指数、利率、居民财产、购物环境等等都可能对居民消费有影响。为了分析什么是影响各地区居民消费支出有明显差异的最主要因素，并分析影响因素与消费水平的数量关系，可以建立相应的计量经济模型去研究。 二、模型设定 我们研究的对象是各地区居民消费的差异。居民消费可分为城市居民消费和农村居民消费，由于各地区的城市与农村人口比例及经济结构有较大差异，最具有直接对比可比性的是城市居民消费。而且，由于各地区人口和经济总量不同，只能用“城市居民每人每年的平均消费支出”来比较，而这正是可从统计年鉴中获得数据的变量。所以模型的被解释变量Y选定为“城市居民每人每年的平均消费支出”。 因为研究的目的是各地区城市居民消费的差异，并不是城市居民消费在不同时间的变动，所以应选择同一时期各地区城市居民的消费支出来建立模型。因此建立的是2002年截面数据模型。 影响各地区城市居民人均消费支出有明显差异的因素有多种，但从理论和经验分析，最主要的影响因素应是居民收入，其他因素虽然对居民消费也有影响，但有的不易取得数据，如“居民财产”和“购物环境”；有的与居民收入可能高度相关，如“就业状况”、“居民财产”；还有的因素在运用截面数据时在地区间的差异并不大，如“零售物价指数”、“利率”。因此这些其他因素可以不列入模型，即便它们对居民消费有某些影响也可归入随即扰动项中。为了与“城市居民人均消费支出”相对应，选择在统计年鉴中可以获得的“城市居民每人每年可支配收入”作为解释变量X。 从2002年《中国统计年鉴》中得到表的数据: 表 2002年中国各地区城市居民人均年消费支出和可支配收入

计量经济学-案例分析-第六章

第六章 案例分析 一、研究目的 2003年中国农村人口占59.47％，而消费总量却只占41.4%，农村居民的收入和消费是一个值得研究的问题。消费模型是研究居民消费行为的常用工具。通过中国农村居民消费模型的分析可判断农村居民的边际消费倾向，这是宏观经济分析的重要参数。同时，农村居民消费模型也能用于农村居民消费水平的预测。 二、模型设定 正如第二章所讲述的，影响居民消费的因素很多，但由于受各种条件的限制，通常只引入居民收入一个变量做解释变量，即消费模型设定为 t t t u X Y ++=21ββ （6.43） 式中，Y t 为农村居民人均消费支出，X t 为农村人均居民纯收入，u t 为随机误差项。表6.3是从《中国统计年鉴》收集的中国农村居民1985-2003年的收入与消费数据。 表6.3 1985-2003年农村居民人均收入和消费 单位： 元

2000 2001 2002 2003 2253.40 2366.40 2475.60 2622.24 1670.00 1741.00 1834.00 1943.30 314.0 316.5 315.2 320.2 717.64 747.68 785.41 818.86 531.85 550.08 581.85 606.81 为了消除价格变动因素对农村居民收入和消费支出的影响，不宜直接采用现价人均纯收入和现价人均消费支出的数据，而需要用经消费价格指数进行调整后的1985年可比价格计的人均纯收入和人均消费支出的数据作回归分析。 根据表6.3中调整后的1985年可比价格计的人均纯收入和人均消费支出的数据，使用普通最小二乘法估计消费模型得 t t X Y 0.59987528.106?+= （6.44） Se = (12.2238) (0.0214) t = (8.7332) (28.3067) R 2 = 0.9788，F = 786.0548，d f = 17，DW = 0.7706 该回归方程可决系数较高，回归系数均显著。对样本量为19、一个解释变量的模型、5%显著水平，查DW 统计表可知，d L =1.18，d U = 1.40，模型中DW

计量经济学-案例分析-第八章

第八章案例分析 改革开放以来，随着经济的发展中国城乡居民的收入快速增长，同时城乡居民的储蓄存 款也迅速增长。经济学界的一种观点认为，20世纪90年代以后由于经济体制、住房、医疗、养老等社会保障体制的变化，使居民的储蓄行为发生了明显改变。为了考察改革开放以来中 国居民的储蓄存款与收入的关系是否已发生变化，以城乡居民人民币储蓄存款年底余额代表 居民储蓄（Y），以国民总收入GNI代表城乡居民收入，分析居民收入对储蓄存款影响的数量关系。 表8.1为1978-2003年中国的国民总收入和城乡居民人民币储蓄存款年底余额及增加额的数据。 单位：亿元 2004 鉴数值，与用年底余额计算的数值有差异。 为了研究1978—2003年期间城乡居民储蓄存款随收入的变化规律是否有变化,考证城

乡居民储蓄存款、国民总收入随时间的变化情况，如下图所示: 图8.5 从图8.5中，尚无法得到居民的储蓄行为发生明显改变的详尽信息。若取居民储蓄的增量 （YY ）,并作时序图（见图 8.6） 从居民储蓄增量图可以看出，城乡居民的储蓄行为表现出了明显的阶段特征: 2000年有两个明显的转折点。再从城乡居民储蓄存款增量与国民总收入之间关系的散布图 看（见图8.7），也呈现出了相同的阶段性特征。 为了分析居民储蓄行为在 1996年前后和2000年前后三个阶段的数量关系，引入虚拟变 量D 和D2°D 和D 2的选择，是以1996>2000年两个转折点作为依据，1996年的GNI 为66850.50 亿元,2000年的GNI 为国为民8254.00亿元，并设定了如下以加法和乘法两种方式同时引入 虚拟变量的的模型: YY = 1+ 2GNI t 3 GNI t 66850.50 D 1t + 4 GNh 88254.00 D 2t i D 1 t 1996年以后 D 1 t 2000年以后 其中: D 1t _ t 1996年及以前 2t 0 t 2000年及以前 对上式进行回归后，有: Dependent Variable: YY Method: Least Squares Date: 06/16/05 Time: 23:27 120000 8.7 1996年和 100000- 40000 2WM GNi o eOB2&ISEea9a9l2949698[Ma2 20CUC ir-“- 1CC0C 图 8.6 *OOCO mnoot ， RtKXD Tconr GF*

计量经济学(英文)重点知识点考试必备

第一章 1.Econometrics（计量经济学）： the social science in which the tools of economic theory, mathematics, and statistical inference are applied to the analysis of economic phenomena. the result of a certain outlook on the role of economics, consists of the application of mathematical statistics to economic data to lend empirical support to the models constructed by mathematical economics and to obtain numerical results. 2.Econometric analysis proceeds along the following lines计量经济学 分析步骤 1)Creating a statement of theory or hypothesis.建立一个理论假说 2)Collecting data.收集数据 3)Specifying the mathematical model of theory.设定数学模型 4)Specifying the statistical, or econometric, model of theory.设立统计或经济计量模型 5)Estimating the parameters of the chosen econometric model.估计经济计量模型参数 6)Checking for model adequacy : Model specification testing.核查模型的适用性：模型设定检验 7)Testing the hypothesis derived from the model.检验自模型的假设 8)Using the model for prediction or forecasting.利用模型进行预测 Step2：收集数据 Three types of data三类可用于分析的数据 1)Time series(时间序列数据):Collected over a period of time, are collected at regular intervals.按时间跨度收集得到

计量经济学-案例分析-第二章

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计量经济学实例分析

计量经济学实例分析 The Standardization Office was revised on the afternoon of December 13, 2020

计量经济学实例分析 -------居民消费水平与GDP之间关系 摘要 改革开放以来，我国居民收入与消费水平不断提高，居民消费需求成为我国经济增长的关键动力，特别是21世纪初以来，居民消费需求对过敏寂静的发展起到了越来越大的作用。及时把握居民消费需求的变化，并制定相关政策推动内需，对于提高我国经济增长速度和质量都有了重要的意义。 凯恩斯认为，短期影响个人消费的主观因素是确定的，消费者的消费主要取决于收入的多少，而其他因素对消费的影响相对较小。因此，本文只对我国居民消费水平和GDP的变化情况之间建立了粗略的模型。 本文利用了1990-2009年之间20年内居民消费水平和GDP数据，旨在说明其中的相互关系，并建立模型以供参考。 关键词 消费收入 GDP 一，理论陈述 1,凯恩斯的绝对收入假说 凯恩斯在《货币通论》中提出了绝对收入假说，即人们的消费支出是起当期的可支配收入决定的。当人们的可支配收入增加时，其中用于消费的数额也会增加，但消费增量在收入增量中的比重是下降的，因此随着收入的增加，人们的消费在收入中的比重是下降的，而储蓄在收入中所占的比重则是上升的。 凯尔斯构建的绝对收入消费函数中，当人们的可支配收入增加时，其中用于消费的数额也会增加，但是消费增量在收入增量中的比重是下降的，因此随着收入的增加，人们的消费在收入中的比重是下降的，而储蓄在收入中的比重则是上升的。 二，实证分析

消费水平是指，一个国家在一定时期内人们在消费过程中对物质文化生活需要的满足程度。 本文以分析居民消费水平为目的，考虑到了GDP 对消费水平的影响，根据学到的计量经济学知识，采用了1990-2009年间的完整数据，构建了以居民收入水平为被解释变量，GDP 为解释变量的一元回归线性模型。 1，参数估计 设模型表达式为：i i i Y U +βX α=+ 其中：Yi ：居民消费水平（元） Xi ：GDP （亿元） Ui ：随机干扰项 表一：居民消费水平与GDP 数据表

(完整版)计量经济学Econometrics专业词汇中英文对照

Econometrics 专业词汇中英文对照（按课件顺序） Ch1-3 Causal effects：因果影响，指的是当x变化时，会引起y的变化；Elasticity：弹性；correlation (coefficient) 相关（系数），相关系数没有单位，unit free； estimation：估计；hypothesis testing：假设检验；confidence interval：置信区间；difference-in-means test：均值差异检验，即检验两个样本的均值是否相同； standard error：标准差；statistical inference：统计推断； Moments of distribution：分布的矩函数；conditional distribution (means)：条件分布（均值）；variance：方差；standard deviation：标准差（指总体方差的平方根）； standard error：标准误差，指样本方差的平方根；skewness：偏度，度量分布的对称性；kurtosis：峰度，度量厚尾性，即度量离散程度；joint distribution：联合分布；conditional expectation：条件期望（指总体）；randomness：随机性 i.i.d., independently and identically distributed：独立同分布的； sampling distribution：抽样分布，指的是当抽取不同的随机样本时，统计量的取值会有所不同，而当取遍所有的样本量为n的样本时，统计量有一个取值规律，即抽样分布，即统计量的随机性来自样本的随机性 consistent (consistency)：相合的（相合性），指当样本量趋于无穷大时，估计量依概率收敛到真实值；此外，在统计的语言中，还有一个叫模型选择的相合性，指的是能依概率选取到正确的模型 Central limit theory：中心极限定理；unbiased estimator：无偏估计量； uncertainty：不确定性；approximation：逼近；least squares estimator：最小二乘估计量；provisional decision：临时的决定，用于假设检验，指的是，我们现在下的结论是基于现在的数据的，如果数据变化，我们的结论可能会发生变化 significance level：显著性水平，一般取0.05或者0.01,0.1，是一个预先给定的数值，指的是在原假设成立的假设下，我们可能犯的错误的概率，即拒绝原假设的概率； p-value：p-值，指的是观测到比现在观测到的统计量更极端的概率，一般p-值很小的时候要拒绝原假设，因为这说明要观测到比现在观测到的统计量更极端的情况的概率很小，进而说明现在的统计量很极端。当p-值小于显著性水平时，在该显著性水平下拒绝原假设 Ch4-5 Linear regression：线性回归；ordinary least squares (OLS)：最小二乘； sample regression line：指的是由样本得到的回归方程；measure of fit：拟合程度的度量；regression R2：回归R平方，指的是Y的方差中被X所解释的部分，属于[0,1]，越接近1，说明拟合越好，其中拟合指的是回归方程对Y的解释程度 standard error of the regression (SER)：回归标准差，越小说明拟合越好 degree of freedom：自由度，指的是可以自由变化的参数个数；outliers：异常值； simple random sampling：简单随机抽样，指的是完全的随机抽样，得到的样本满足独立同分布的性质 t-statistics：t统计量；two-sided hypothesis：双边假设检验，指的是被择假设是双边的；null hypothesis：原假设，零假设；alternative hypothesis：被择假设，对立于原假设binary：0、1的分布；homoskedasticity:同方差的，可以写成homogeneity；