The question is as follows

1. (a) The following table gives the sample autocorrelation coefficients and partial autocorre- lation coefficients for a time series with 100 observations. k 1 2 3 4 5 6 7 8 Pk -0.35 -0.17 0.09 -0.06 0.01 -0.01 -0.04 0.07 Okk -0.35 -0.34 0.25 -0.18 -0.11 -0.13 -0.14 0.05 Based on the above information, suggest an ARMA model for the data. Explain your answer. (b) i. Given the AR(2) process Xt = 0.3Xt-1 + 0.04Xt-2 + at, where at is white noise. Is the process stationary? Calculate p1. ii. Using the difference equation approach, find the general expression for pr, k 2 2