babaofanyuan 发表于 2015-5-15 23:27 
您好!!请问 两个变量联合显著的F值在统计上怎么运算 他等于什么呢?
比如 xtreg y x xsquare X2 X3
...
可以手动计算出F统计量的
F test for exclusion restriction
• Exclusion restriction: βj =0
• t test: test whether one variable has effect or not
• F test: test whether one group of variables have effect or not
H0: β1 =0, β2 =0
1. Run an unrestricted regression, and get SSRu , Ru2
log(wage)=β0 +β1 college +β2 univ +β3 exper+u
2. Run an restricted regression, and get SSRr , Rr2
log(wage)=β0 +β3 exper+u
3. Calculate F statistics
F=[(SSRr-SSRu)/q]/[SSRu/n-K-1)]
4.get p value