a) Consider a series that follows a MA(1) process with zero mean and a moving average coefficient of 0.5. What is the value of the autocorrelation function at lag 1 and lag 3 ? marks) b) What is meant by weak stationarity? ( 6 marks) c) Is the following model covariance stationary? Explain (No need to prove). ( 6 marks) Figure 2 Hypothetical forecasting time series (6 periods) xt=+xt1+t where 1 is a white noise. d) In the Dickey-Fuller model: yt=yt1+et here the true value of is equal to zero. Explain why you cannot use a standard t-test to examine if equal to zero. (6 marks) e) Suppose a series is named SM. How do you conduct the Dickey Fuller test by Eviews? Assume that there is an intercept in the alternative hypothesis. (6 marks) a) Consider a series that follows a MA(1) process with zero mean and a moving average coefficient of 0.5. What is the value of the autocorrelation function at lag 1 and lag 3 ? marks) b) What is meant by weak stationarity? ( 6 marks) c) Is the following model covariance stationary? Explain (No need to prove). ( 6 marks) Figure 2 Hypothetical forecasting time series (6 periods) xt=+xt1+t where 1 is a white noise. d) In the Dickey-Fuller model: yt=yt1+et here the true value of is equal to zero. Explain why you cannot use a standard t-test to examine if equal to zero. (6 marks) e) Suppose a series is named SM. How do you conduct the Dickey Fuller test by Eviews? Assume that there is an intercept in the alternative hypothesis. (6 marks)