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Linear Time Series Models for Stationary data - Feweb

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Key concept: SACF, White Noise (WN)<br />

Consistent estimates <strong>for</strong> mean, variance and covariances <strong>for</strong> weakly<br />

stationary processes are obtained as follows:<br />

µ = ¯y, γk = 1<br />

n<br />

n<br />

t=k+1<br />

(yt − ¯y)(yt−k − ¯y).<br />

γk, k = 0, 1, 2, . . . is the sample autocovariance function (SACF).<br />

Simplest example of a stationary series is a White Noise process<br />

(WN) which we denote as εt. WN is a sequence of uncorrelated<br />

random variables with constant mean and variance:<br />

γ0 = σ 2 ε, γk = 0, k = 1, 2, . . ..<br />

Chapter 7.1 Heij et al, TI Econometrics II 2006/2007 – p. 7/24

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