You are given the following time-series model: X_t = 0.8 X_{t-1} + 2 + Z_t - 0.5 Z_{t-1}. Which of the following statements about this model is false? A. ?_X(1) = 0.4. B. ?_X(k) < ?_X(1), k ? 2. C. The model is ARMA(1,1). D. The model is stationary. E. The mean, ?_X, is 2.
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The ACF for an ARMA(1,1) model is given by: Ļ(1) = Ļ1 / (1 + Īø1) In this case, Ļ1 = 0.8 and Īø1 = 0.5. Therefore, Ļ(1) = 0.8 / (1 + 0.5) = 0.8 / 1.5 = 0.5333 ** Show moreā¦
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