Serial correlation is when E[u_i u_j] = 0 for all i $\neq$ j.

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Quizplus · Accepted Answer

Serial correlation, also known as autocorrelation, refers to the correlation of a variable with itself at two points in time. The given equation, suggesting equality to zero for all $i \neq j$, describes a lack of correlation between different observations, not serial correlation. Serial correlation would be concerned with the relationship of $u_t$ with $u_{t-1}$, $u_{t-2}$, etc., for the same variable over time.

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Serial Correlation Is When E[u_i U_j] = 0 for All $\neq$