University of Canterbury
Mid-year Examinations 2016
Prescription Number(s): STAT317-16S1 / ECON323-16S1 Paper Title: Time Series Methods
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Number of Pages: 3
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QUESTIONS START ON PAGE 3
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2 STAT317-16S1/ECON323-16S1
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QUESTION 1
What are the invertibility and stationarity conditions for an ARMA process? Explain the reasons and the importance for such conditions.
QUESTION 2
QUESTION 5
Given the moving average process:
x z 0.7z 0.5z z ~N(0,2),
t t t1 t2 t
Find the values ( k ) of the autocorrelation function for k=1,2,3.
QUESTION 4
Illustrate the major steps of the classical decomposition of a time series.
3 STAT317-16S1/ECON323-16S1
QUESTION 3
Identify the order of the following ARMA(p,q) models and determine whether they are causal and/or invertible:
xt 0.8xt1 0.15 xt2 zt 0.3zt1 ; xt xt1 0.5xt2 zt zt1 ;
~ N (0, 2 ) . Please show all your workings. Assignment Project Exam Help
Explain why differencing a time series you remove a deterministic trend and why you
QUESTION 6
Show that an invertible MA(k) model for any integer value of k is equivalent to an AR of infinite order and that a causal AR(k) model for any integer value of k is equivalent to a MA of infinite order.
should not difference more than twice.
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