Yt = €t – 0.5ɛt–1 + 0.5€t-2 Et ~ WN (0, 1) (a) Find E(y) and Var(y.). (b) Find Cor(yt, Yt–1) and Cor(yt, Yt-2). (c) Is the model above covariance stationary?

MATLAB: An Introduction with Applications
6th Edition
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Author:Amos Gilat
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Chapter1: Starting With Matlab
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Consider the following model:

The text presents a time series model and asks questions regarding its statistical properties.

### Model Description:
The given time series model is:

\[ 
y_t = \varepsilon_t - 0.5\varepsilon_{t-1} + 0.5\varepsilon_{t-2} 
\]

where \(\varepsilon_t\) is a white noise process:

\[ 
\varepsilon_t \sim WN(0,1) 
\]

### Questions:

(a) **Find \(E(y_t)\) and \(Var(y_t)\).**

(b) **Find \(Cor(y_t, y_{t-1})\) and \(Cor(y_t, y_{t-2})\).**

(c) **Is the model above covariance stationary?**

### Explanation:
- **\(E(y_t)\)** refers to the expected value or mean of \(y_t\).
- **\(Var(y_t)\)** refers to the variance of \(y_t\), a measure of the dispersion of the series.
- **\(Cor(y_t, y_{t-1})\)** and **\(Cor(y_t, y_{t-2})\)** refer to the correlation between \(y_t\) and its lagged values, which help in understanding the temporal dependence structure of the series.
- **Covariance Stationarity** requires constant mean, constant variance, and constant autocovariance that depends only on lag for the series.
Transcribed Image Text:The text presents a time series model and asks questions regarding its statistical properties. ### Model Description: The given time series model is: \[ y_t = \varepsilon_t - 0.5\varepsilon_{t-1} + 0.5\varepsilon_{t-2} \] where \(\varepsilon_t\) is a white noise process: \[ \varepsilon_t \sim WN(0,1) \] ### Questions: (a) **Find \(E(y_t)\) and \(Var(y_t)\).** (b) **Find \(Cor(y_t, y_{t-1})\) and \(Cor(y_t, y_{t-2})\).** (c) **Is the model above covariance stationary?** ### Explanation: - **\(E(y_t)\)** refers to the expected value or mean of \(y_t\). - **\(Var(y_t)\)** refers to the variance of \(y_t\), a measure of the dispersion of the series. - **\(Cor(y_t, y_{t-1})\)** and **\(Cor(y_t, y_{t-2})\)** refer to the correlation between \(y_t\) and its lagged values, which help in understanding the temporal dependence structure of the series. - **Covariance Stationarity** requires constant mean, constant variance, and constant autocovariance that depends only on lag for the series.
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