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Published byJemimah Loren Marsh Modified over 9 years ago
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Properties of the estimates of the parameters of ARMA models
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AR(1) models Comparison of Yule-Walker, Least Squares and Maximum Likelihood
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a=0.5, N=20, 50 simulations YW: average 0.44, st.dev. 0.183 LS: average 0.467, st.dev. 0.191 ML: average 0.463, st.dev. 0.19
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a=0.5, N=100, 50 simulations YW: average 0.494, st.dev. 0.086 LS: average 0.498, st.dev. 0.086 ML: average 0.498, st.dev. 0.85
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a=0.5, N=500, 50 simulations YW: average 0.495, st.dev. 0.039 LS: average 0.496, st.dev. 0.04 ML: average 0.496, st.dev. 0.04
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a=0.5, N=1000, 50 simulations YW: average 0.499, st.dev. 0.027 LS: average 0.499, st.dev. 0.027 ML: average 0.499, st.dev. 0.0271
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a=0.95, N=20, 50 simulations YW: average 0.837, st.dev. 0.118 LS: average 0.877, st.dev. 0.126 ML: average 0.882, st.dev. 0.117
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a=0.95, N=100, 50 simulations YW: average 0.918, st.dev. 0.062 LS: average 0.929, st.dev. 0.06 ML: average 0.928, st.dev. 0.055
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a=0.95, N=500, 50 simulations YW: average 0.942, st.dev. 0.015 LS: average 0.944, st.dev. 0.015 ML: average 0.945, st.dev. 0.015
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a=0.95, N=1000, 50 simulations YW: average 0.948, st.dev. 0.011 LS: average 0.949, st.dev. 0.011 ML: average 0.949, st.dev. 0.011
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a=-0.95, N=20, 50 simulations YW: average -0.796, st.dev. 0.165 LS: average -0.855, st.dev. 0.171 ML: average -0.841, st.dev. 0.164
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a=-0.95, N=100, 50 simulations YW: average -0.926, st.dev. 0.037 LS: average -0.935, st.dev. 0.04 ML: average -0.932, st.dev. 0.038
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a=-0.95, N=500, 50 simulations YW: average -0.938, st.dev. 0.019 LS: average -0.941, st.dev. 0.018 ML: average -0.941, st.dev. 0.018
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a=-0.95, N=1000, 50 simulations YW: average -0.948, st.dev. 0.011 LS: average -0.949, st.dev. 0.012 ML: average -0.949, st.dev. 0.012
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AR(2) models Yule-Walker, Least squares and Maximum Likelihood for different N
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N=20
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a 1 = -1.8, a 2 = 0.9, N=20 Yule-Walker
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a 1 = -1.8, a 2 = 0.9, N=20 Least Squares
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a 1 = -1.8, a 2 = 0.9, N=20 Maximum Likelihood
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a 1 = 0.05, a 2 = -0.9, N=20 Yule-Walker
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a 1 = 0.05, a 2 = -0.9, N=20 Least Squares
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a 1 = 0.05, a 2 = -0.9, N=20 Maximum Likelihood
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N=100
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a 1 = -1.8, a 2 = 0.9, N=100 Yule-Walker
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a 1 = -1.8, a 2 = 0.9, N=100 Least Squares
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a 1 = -1.8, a 2 = 0.9, N=100 Maximum Likelihood
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N=1000
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a 1 = 0.05, a 2 = -0.9, N=1000 Yule-Walker
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a 1 = 0.05, a 2 = -0.9, N=1000 Least Squares
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a 1 = 0.05, a 2 = -0.9, N=1000 Maximum Likelihood
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AR(2) models Maximum Likelihood for different combinations of a 1, a 2
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a 1 = -1, a 2 = 0.5, N=20
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a 1 = -1, a 2 = 0.5, N=100
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a 1 = -1, a 2 = 0.5, N=1000
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a 1 = 1.3, a 2 = 0.8, N=20
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a 1 = 1.3, a 2 = 0.8, N=100
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a 1 = 1.3, a 2 = 0.8, N=1000
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MA(1) models Conditional Likelihood for different b and N
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b = 0.9
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b = 0.6
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b = -0.4
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b = -0.9
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b = -1 (not invertible, still stationary)
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Here true model is MA(2) with ρ 1 about 0.7. Estimated b is, on average, about 0.75 (corresponding ρ 1 = 0.48)
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ARMA(1,1) models Conditional Likelihood for different a, b and N
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a = 0.8, b = 0.75
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N=20
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N=50
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N=100
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a = -0.7, b = -0.65
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N=20
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N=50
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N=100
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a = 0.8, b = -0.75 (practically a white noise)
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N=20
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N=50
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N=100
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