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Advanced Proof

Derivation of the Variance of the l-step Ahead Forecast Error for a General ARMA(p,q) Process

Students often confuse the forecast error ψl \psi_l with the process itself Xt X_t or misinterpret the summation as being over p p or q q directly, rather than the innovations Zt Z_t .
Institutional Reference: Time Series Analysis
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