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Estimating the Codifference Function of Linear Time Series Models ...

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Table 1: The true values I(·) and <strong>the</strong> estimates Î(·)<br />

N α Method s I(1) Avg. Î(1) MAD 1 I(2) Avg. Î(2) MAD 2<br />

100 2 Avg. {0.01} 0.66180 0.04600 0.14647 0.10186<br />

Exp. {0.01, 0.1,1} 0.67722 0.63195 0.05732 0.17821 0.19387 0.09025<br />

ACF - 0.65848 0.04644 0.14500 0.10115<br />

1.8 Avg. {0.01, 0.2} 0.64700 0.64938 0.04415 0.19237 0.15860 0.09297<br />

Exp. {0.01, 0.1,1} 0.62509 0.04760 0.20409 0.08011<br />

1.5 Avg. {0.01, 0.1, 0.2} 0.59903 0.60826 0.04839 0.21343 0.17158 0.07927<br />

Exp. {0.01, 0.1,1} 0.59728 0.04888 0.21062 0.06729<br />

1.3 Avg. {0.01, 0.06, . . . ,0.21} 0.56554 0.57235 0.05032 0.22665 0.19017 0.06974<br />

Exp. {0.01, 0.1,1} 0.57364 0.05548 0.22380 0.06105<br />

1 Avg. {0.01, 0.02, . . . ,0.2} 0.51350 0.50708 0.04745 0.24325 0.21576 0.06049<br />

Exp {0.01, 0.02, . . . ,0.2} 0.50717 0.04739 0.21577 0.06036<br />

0.8 Avg. {0.01, 0.02, . . . ,0.1} 0.47792 0.47274 0.04357 0.25014 0.22644 0.05599<br />

Exp. {0.01, 0.02, . . . ,0.1} 0.47276 0.04355 0.22643 0.05597<br />

0.5 Avg. {0.01, 0.02, . . . ,0.1} 0.42379 0.40713 0.04463 0.24809 0.22776 0.06033<br />

Exp. {0.01, 0.02, . . . ,0.1} 0.40715 0.04459 0.22776 0.06028<br />

1000 2 Avg. {0.01} 0.67577 0.01335 0.17495 0.03096<br />

Exp. {0.01} 0.67722 0.67577 0.01335 0.17821 0.17495 0.03096<br />

ACF - 0.67544 0.01336 0.17477 0.03094<br />

1.8 Avg. {0.01, 0.06, . . . ,0.21} 0.64700 0.65059 0.01645 0.19237 0.18859 0.02708<br />

Exp. {0.01, 0.06, . . . ,0.21} 0.65067 0.01649 0.18854 0.02708<br />

1.5 Avg. {0.01, 0.02, . . . ,0.2} 0.59903 0.60204 0.01815 0.21343 0.20879 0.02155<br />

Exp. {0.01, 0.02, . . . ,0.2} 0.60209 0.01822 0.20878 0.02154<br />

1.3 Avg. {0.01, 0.02, . . . ,0.2} 0.56554 0.56751 0.01640 0.22665 0.22312 0.01996<br />

Exp {0.01, 0.02, . . . ,0.2} 0.56754 0.01644 0.22310 0.01992<br />

1 Avg. {0.01, 0.02, . . . ,0.1} 0.51350 0.51396 0.01521 0.24325 0.24105 0.01577<br />

Exp. {0.01, 0.02, . . . ,0.1} 0.51396 0.01521 0.24105 0.01576<br />

0.8 Avg. {0.01, 0.02, . . . ,0.1} 0.47792 0.47742 0.01383 0.25014 0.24811 0.01511<br />

Exp. {0.01, 0.02, . . . ,0.1} 0.47742 0.01382 0.24811 0.01510<br />

0.5 Avg. {0.01, 0.02, . . . ,0.1} 0.42379 0.42239 0.01296 0.24809 0.24548 0.01852<br />

Exp. {0.01, 0.02, . . . ,0.1} 0.42239 0.01295 0.24548 0.01851<br />

The true values I(·) and <strong>the</strong> estimates Î(·) from <strong>the</strong> experiment I, that is MA(2) process with c0 = 1,<br />

c 1 = 2 and c 2 = 1.111 for T = 1000 replication, and for some sample size N. The ǫ t is SαS process<br />

with some α and σ = 1. Here, Avg.Î(i) = ∑ 1 T<br />

T j=1 ReÎ(i)j, and MADi = ∑ 1 T<br />

T j=1<br />

|ReÎ(i)j − I(i)|,<br />

i = 1,2, where ReÎ(i) j denotes <strong>the</strong> estimates at lag i in run j . The weighting methods here denote by<br />

<strong>the</strong> simple average (method Avg.) and <strong>the</strong> negative exponential weighted average (method Exp.). Fur<strong>the</strong>r<br />

explanation about <strong>the</strong> table is given in Section 3.2<br />

21

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