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Answers for “ARIMA(1,1,1) 的方程是什么?”

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The equation for ARIMA(1,1,1) is Zt=ϕ1Zt−1+θ1ϵt−1+ϵtZ_t = \phi_1 Z_{t-1} + \theta_1 \epsilon_{t-1} + \epsilon_t, where ZtZ_t is the differenced series, ϕ1\phi_1 is the autoregressive coefficient, θ1\theta_1 is the moving-average coefficient, and ϵt\epsilon_t is the error term.

Conditions: The model is ARIMA(1,1,1).; ZtZ_t is the first difference of the original series qtq_t.; p=1,d=1,q=1p=1, d=1, q=1.

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An ARIMA(1,1,1) model consists of taking a first difference of the original series and then fitting an ARMA(1,1) model to the resulting differenced series. The equations are Yt−Yt−1=WtY_t - Y_{t-1} = W_t and Wt=ω+ϕ1Wt−1+θ1et−1+etW_t = \omega + \phi_1 W_{t-1} + \theta_1 e_{t-1} + e_t.

Conditions: p=1p=1 (one AR term); d=1d=1 (one first difference); q=1q=1 (one MA term)

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The dd in ARIMA(p,d,q) represents the order of differencing, also known as the integrated component. It indicates how many times the original series has been differenced to achieve stationarity.

Conditions: The model is denoted as ARIMA(p,d,q).; dd is a non-negative integer.

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The I in ARIMA stands for Integrated. It is implemented by modeling the differences of the original time series rather than the raw series itself.

Conditions: The context is the ARIMA time series model.; The explanation refers to the specific ARIMA(1,1,1) example shown on the board.

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In ARIMA(p, d, q), p represents the number of autoregressive (AR) terms, d is the number of first differences applied to make the data stationary, and q denotes the number of moving average (MA) terms.

Conditions: Applies to ARIMA model notation.