The Error Term Is Homoskedastic If A $\operatorname { var } \left( u _ { i } \mid X _ { i } = x \right)$

Short Answer

The error term is homoskedastic if a. $\operatorname { var } \left( u _ { i } \mid X _ { i } = x \right)$ is constant for $i = 1 , \ldots , n$
b. $\operatorname { var } \left( u _ { i } \mid X _ { i } = x \right)$ depends on $x$
c. $X _ { i }$ is normally distributed
d. there are no outliers.