应用回归分析_整理课后习题答案
假设2、随机误差项ε具有零均值、同方差和不序列相关性:E(\xi _{i})=0i=1,2, \dotsc ,nVar(a)= \sigma ^{2}i=1,2, \dotsc ,nCov(\xi _{i}, \xi _{j})=0iji,j=1,2, \dotsc ,n假设3、随机误差项ε与解释变量X之间不相关:Cov(X_{f}^{ \infty }_{i})=0i=1,2, \dotsc ,n假设4、ε服从零均值、同方差、零协方差的正态分布\xi _{i} \sim N(0, \sigma ^{2})i=1,2, \dotsc ,n2.2考虑过原点的线性回归模型Y_{i}= \beta _{1}X_{i}+\xi _{i}i=1,2, \cdots ,n误差\xi _{i}(i=1,2, \cdots ,n)仍满足基本假定。求\beta _{1}的最小二乘估计解:Q_{e}= \sum _{i=1}^{n}(Y_{i}- \hat {Y_{i}})^{2}= \sum _{i=1}^{n}(Y_{i}- \hat { \beta _{1}}\frac { \partial Q_{e}}{ \partial \hat { \beta }_{1}}=-2 \sum _{i=1}^{n}(Y_{i}- \hat { \beta }_{1}X_{i})X_{i}=0得:\hat { \beta _{1}}= \frac { \sum \limits _{i=1}^{n}(X_{i}Y_{i})}{ \sum \limits _{i=1}^{n}(X_{i}^{2})}2.3证明(2.27式),\sum e_{i}=0, \sum e_{i}X_{i}=0。证明:Q= \sum _{1}^{n}(Y_{i}- \hat Y_{i})^{2}= \sum _{1}^{n}(Y_{i}-(\hat \beta _{0}+\hat \beta _{1}X_{i其中:\hat {Y}_{i}= \hat { \beta }_{0}+\hat { \beta }_{1}X_{i}e_{i}=Y_{i}- \hat {Y}_{i} \frac { \partial Q}{ \partial \hat { \beta }_{\cases { \s