Cov $\left( u _ { i t } , u _ { i s } \mid X _ { i t } , X _ { i s } \right) = 0 \text { for } t \neq s$

question 34

Multiple Choice

cov $\left( u _ { i t } , u _ { i s } \mid X _ { i t } , X _ { i s } \right) = 0 \text { for } t \neq s$
means that

• A) there is no perfect multicollinearity in the errors.
• B) division of errors by regressors in different time periods is always zero.
• C) there is no correlation over time in the residuals.
• D) conditional on the regressors, the errors are uncorrelated over time.

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