Consider the following processes and verify if they are causal, stationary and invertible, (a) yt 􀀀 0:4yt􀀀1 + 0:03yt􀀀2 = "t, where "t are independent random variables with Student t distribution of...

Consider the following processes and verify if they are causal, stationary

and invertible,

(a) yt 􀀀 0:4yt􀀀1 + 0:03yt􀀀2 = "t, where "t are independent random variables

with Student t distribution of 6 degree of freedom.

(b) yt = "t+1+0:45"t, where "t is a white noise sequence with distribution

N(0; 1).

(c) yt = "t P1 j=1 _j􀀀1"t􀀀j , where "t is a white noise sequence

with variance _2 " , j_j 1 and j_j 1.