人大时间序列课后习
第二章P34
1、(1)因为序列具有明显的趋势,所以序列非平稳。
(2)样本自相关系数:
,nk
(x,x)(x,x),,ttk,(k),1tˆ, ,,kn(0),2(x,x),t,1t
n11 x,x,(1,2,?,20),10.5,tn20,1t
2012 ,(0),(x,x),35 ,t20t,1
191 ,(1),(x,x)(x,x),29.75 ,tt,119t,1
181 ,(2),(x,x)(x,x),25.9167 ,tt,218t,1
171 ,(3),(x,x)(x,x),21.75 ,tt,317t,1
(4)=17.25 (5)=12.4167 (6)=7.25 ,,,
=0.85(0.85) =0.7405(0.702) =0.6214(0.556) ,,,231
=0.4929(0.415) =0.3548(0.280) =0.2071(0.153) ,,,456注:括号内的结果为近似公式所计算。
(3)样本自相关图:
Autocorrelation Partial Correlation AC PAC Q-Stat Prob
. |*******| . |*******| 1 0.850 0.850 16.732 0.000
. |***** | . *| . | 2 0.702 -0.076 28.761 0.000
. |**** | . *| . | 3 0.556 -0.076 36.762 0.000
. |*** | . *| . | 4 0.415 -0.077 41.500 0.000
. |**. | . *| . | 5 0.280 -0.077 43.800 0.000
. |* . | . *| . | 6 0.153 -0.078 44.533 0.000
. | . | . *| . | 7 0.034 -0.077 44.572 0.000
. *| . | . *| . | 8 -0.074 -0.077 44.771 0.000
. *| . | . *| . | 9 -0.170 -0.075 45.921 0.000
.**| . | . *| . | 10 -0.252 -0.072 48.713 0.000
.**| . | . *| . | 11 -0.319 -0.067 53.693 0.000
***| . | . *| . | 12 -0.370 -0.060 61.220 0.000 该图的自相关系数衰减为0的速度缓慢,可认为非平稳。
2m,,ˆ,k,,LBnn,,(2)4、 ,,,nk,,1k,,
LB(6)=1.6747 LB(12)=4.9895
22 (6)=12.59 (12)=21.0 ,,0.050.05
显然,LB统计量小于对应的临界值,该序列为纯随机序列。
第三章P97
1、解: E(x),0.7*E(x),E(,)tt,1t
(1,0.7)E(x),0E(x),0tt
(1,0.7B)x,,tt
,122 x,(1,0.7B),,(1,0.7B,0.7B,?),ttt
122 Var(x),,,1.9608,t,,1,0.49
2 ,,,,,0.49,,021022
2、解:对于AR(2)模型:
,,,,,,,,,,,,,0.5,11021121, ,,,,,,,,,,,,,,0.321120112,
,,7/15,1解得: ,,,1/152,
3、解:根据该AR(2)模型的形式,易得: E(x),0t
原模型可变为: x,0.8x,0.15x,,tt,1t,2t
1,,22(), Varx,t(1,)(1,,)(1,,),,,,,21212
(1,0.15)22, =1.9823 ,,(1,0.15)(1,0.8,0.15)(1,0.8,0.15)
,,,,,,/(1,),0.6957,,0.6957,,112111,,,,,,,,, ,,,0.4066,,,0.15,,21120222
,,,,,,,,,,,0.2209,03122133,,
4、解:原模型可变形为:
2(1,B,cB)x,, tt
由其平稳域判别条件知:当,且时,模型平稳。 |,|,1,,,,1,,,,122121
由此可知c应满足:,且 |c|,1c,1,1c,1,1
即当,1