(a) What do you understand by the term ‘autocorrelation’?
(b) An econometrician suspects that the residuals of her model might be auto correlated. Explain the steps involved in testing this theory using the Durbin–Watson (DW) test.
(c) The econometrician follows your guidance (!!!) in part (b) and calculates a value for the Durbin–Watson statistic of 0.95. The regression has 60 quarterly observations and three explanatory
variables (plus a constant term). Perform the test. What is your conclusion?
(d) In order to allow for autocorrelation, the econometrician decides to use a model in first differences with a constant
(e) The econometrician finally settles on a model with both first differences and lagged levels terms of the variables
Can the Durbin–Watson test still validly be used in this case?