CH7_ultiple Regression Analysis with Qualitative Information_Dummy Variables_C1.ppt

CHAPTER 6公共管理常见模型的设定 Risk varies inversely with knowledge. Irving Fisher: The theory of Interest (1930) Highlights Most of this chapter is dedicated to qualitative independent variables. We’ll show how qualitative explanatory variables can be easily incorporated into multiple regression models. We’ll discuss a binary dependent variable, which is a particular kind of qualitative dependent variable, the linear probability model. 6.1 政策分析与虚拟变量（DESCRIBING QUALITATIVE INFORMATION） 表示具有或不具有某种属性的变量被称为虚拟变量（Variables indicate the presence or absence of a quality or an attribute are most commonly called dummy variables.） 可以用0或1定义虚拟变量。One way we could quantity such attributes is by constructing artificial variables that take on values of 1 or 0, 1 indicating the presence of that attribute, and 0 indicating the absence of that attribute. 虚拟变量可以对事物进行分类。Such variables are thus essentially a device to classify data into mutually exclusive categories. When you can measure what you are speaking about, and express it in numbers, you know something about it; when you cannot measure it, when you cannot measure it in numbers, your knowledge is of a meager and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science. Lord Kelvin 6.2 单个虚拟自变量（A SINGLE DUMMY INDEPENDENT VARIABLE） In the simplest case, with only a single dummy explanatory variable, we just add it as an independent variable in the equation. ?0 is the difference in hourly wage between females and males, given the same amount of education (and the same error term u). When you can measure what you are speaking about, and express it in numbers, you know something about it; when you cannot measure it, when you cannot measure it in numbers, your knowledge is of a meager and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to t