Figure 5.40, the MA(1) models, did not appear to be the optimum but ARMA(1.2) did 
by AlC criteria. Accordingly, the spectrum of ARMA(1.2) fitted as optimum is shown as 
spectrum Fig. 5.40b, and for reference, the spectrum of fitted MA(1) even though it did 
not appear to be optimum is shown as Fig. 5.40e. 
6.25 5 
4 
5.00 4 
1 Bo OY 
Sh) S| oe = 
H 
2.50 4 
1.254 
Fig. 5.40a. Theoretical MA(1). 
Fig. 5.40. Spectrum for MA(1) process (2) X,=€,+0.7€.,,  €: N[0, 1]. 
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