Chapter 1 Introduction 1.1 What is econometrics? Application of st atistical and mathematical met hods to the analysis of economic Purposes 1. Testing economic theories 2. Policy analysis(simultaneous equations model, vector autoregressive model
General linear models Suppose that we have a model: 1 It is inherently linear for the parameters if it can be transformed into Examples: 1. Exponential model: Y
1. Recall the assumption for the CMLRM: (Homoskedasticity) 2. Counterexamples 1、rich family and poor family expenditures; 2、large company and small company sales. There exists heteroskedasticity in lots of econometric problems