Properties of the estimates of the parameters of ARMA models
AR(1) models Comparison of Yule-Walker, Least Squares and Maximum Likelihood
a=0.5, N=20, 50 simulations YW: average 0.44, st.dev LS: average 0.467, st.dev ML: average 0.463, st.dev. 0.19
a=0.5, N=100, 50 simulations YW: average 0.494, st.dev LS: average 0.498, st.dev ML: average 0.498, st.dev. 0.85
a=0.5, N=500, 50 simulations YW: average 0.495, st.dev LS: average 0.496, st.dev ML: average 0.496, st.dev. 0.04
a=0.5, N=1000, 50 simulations YW: average 0.499, st.dev LS: average 0.499, st.dev ML: average 0.499, st.dev
a=0.95, N=20, 50 simulations YW: average 0.837, st.dev LS: average 0.877, st.dev ML: average 0.882, st.dev
a=0.95, N=100, 50 simulations YW: average 0.918, st.dev LS: average 0.929, st.dev ML: average 0.928, st.dev
a=0.95, N=500, 50 simulations YW: average 0.942, st.dev LS: average 0.944, st.dev ML: average 0.945, st.dev
a=0.95, N=1000, 50 simulations YW: average 0.948, st.dev LS: average 0.949, st.dev ML: average 0.949, st.dev
a=-0.95, N=20, 50 simulations YW: average , st.dev LS: average , st.dev ML: average , st.dev
a=-0.95, N=100, 50 simulations YW: average , st.dev LS: average , st.dev ML: average , st.dev
a=-0.95, N=500, 50 simulations YW: average , st.dev LS: average , st.dev ML: average , st.dev
a=-0.95, N=1000, 50 simulations YW: average , st.dev LS: average , st.dev ML: average , st.dev
AR(2) models Yule-Walker, Least squares and Maximum Likelihood for different N
N=20
a 1 = -1.8, a 2 = 0.9, N=20 Yule-Walker
a 1 = -1.8, a 2 = 0.9, N=20 Least Squares
a 1 = -1.8, a 2 = 0.9, N=20 Maximum Likelihood
a 1 = 0.05, a 2 = -0.9, N=20 Yule-Walker
a 1 = 0.05, a 2 = -0.9, N=20 Least Squares
a 1 = 0.05, a 2 = -0.9, N=20 Maximum Likelihood
N=100
a 1 = -1.8, a 2 = 0.9, N=100 Yule-Walker
a 1 = -1.8, a 2 = 0.9, N=100 Least Squares
a 1 = -1.8, a 2 = 0.9, N=100 Maximum Likelihood
N=1000
a 1 = 0.05, a 2 = -0.9, N=1000 Yule-Walker
a 1 = 0.05, a 2 = -0.9, N=1000 Least Squares
a 1 = 0.05, a 2 = -0.9, N=1000 Maximum Likelihood
AR(2) models Maximum Likelihood for different combinations of a 1, a 2
a 1 = -1, a 2 = 0.5, N=20
a 1 = -1, a 2 = 0.5, N=100
a 1 = -1, a 2 = 0.5, N=1000
a 1 = 1.3, a 2 = 0.8, N=20
a 1 = 1.3, a 2 = 0.8, N=100
a 1 = 1.3, a 2 = 0.8, N=1000
MA(1) models Conditional Likelihood for different b and N
b = 0.9
b = 0.6
b = -0.4
b = -0.9
b = -1 (not invertible, still stationary)
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)
ARMA(1,1) models Conditional Likelihood for different a, b and N
a = 0.8, b = 0.75
N=20
N=50
N=100
a = -0.7, b = -0.65
N=20
N=50
N=100
a = 0.8, b = (practically a white noise)
N=20
N=50
N=100