2.1 1、Statistical or random experiment 2、Sample space or population Sample point, event 2.2 Stochastic or random variable (r. v.) 2.3 Probability 2.4 R.V. and probability density function
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
1. Single equation estimation procedures Indirect least squares(ILS)(恰好识别) Two- -stage least squares(2SLS)(过度识别) 2. System estimation procedures Three-stage- least squares(sLS)(跨方程相 关) In1962 Theil and Zellner first proposed this method. 2SLS+GLS= 3SLS (gls=generalized least squares)