1. Which of the following best describes the autocorrelation function (ACF) of a non-stationary time series?

a.All of the options are correct.

b. The ACF has several significant spikes.

c. The null of zero autocorrelation is rejected for a significant amount of lags.

d. The ACF has coefficients that very gradually go to zero.

e. The ACF has a spurious pattern of spikes as lags increase.

2. Which of the following models utilizes a transformed series to induce a stationary series?

a. ARIMA(1, 0, 1)

b. ARIMA(1, 0, 0)

c. None of the options are correct.

d. ARIMA(0, 0, 1)

e. ARIMA(1, 1, 1)

3.A time series that can be best represented as a MA(2) model has a partial autocorrelation function that

a. exponentially declines to zero as lag length increases.

b. All of the options are correct.

c. has one large positive spike and then goes to zero.

d. cyclically declines to zero as lag length increases.

e. has one large negative spike and then goes to zero.