问题如下：
If an omitted variable is correlated with variables already included in the model, coefficient estimates will be biased and inconsistent and standard errors will also be inconsistent. Is this Statement correct?
选项：
A.Yes.
B.No, because the model’s coefficient estimates will be unbiased.
C.No, because the model’s coefficient estimates will be consistent.
解释：
A is correct.
Chang is correct because a correlated omitted variable will result in biased and inconsistent parameter estimates and inconsistent standard errors.
上课时候就有这个疑问
课上说if omitted variable is x2:
假设原来是y=b0+b1x1+b2x2+E
现在是y=a0+a1x1+e
课上说x2是被包含在e里, 即e(error项)与x1有相关性，这个说法不是和conditional heteroskedasticity一样么？
conditional heteroskedasticity得出的结论是coefficient estimates不受影响，但这里说忽略了x2会使得coefficient estimates unreliable...
请问我的理解是在哪一步出现了问题？是这里不能类比么？
