The residuals for 15 consecutive time periods are as follows:

a. Plot the residuals over time. What conclusion can you reach about the pattern of the residuals over time?
b. Compute the Durbin-Watson statistic. At the 0.05 level of significance, is there evidence of positive autocorrelation among the residuals?
c. Based on (a) and (b), what conclusion can you reach about the autocorrelation of the residuals?