A logistics company records last year’s monthly long-distance phone-call costs as follows (in dollars):

The regression equation is Predicted Costs = 968.5152 +
24.9336 Month.

a) Find the residuals.

b) Plot the residuals against Month. Comment.

c) Compute the Durbin-Watson statistic.

d) At a = 0.05, what are the values of dL and dU?

e) Is there evidence of positive autocorrelation? Explain.

f) Is there evidence of negative autocorrelation? Explain.

Transcribed Image Text:

Month Cost ($) January 1048 February 961 March 1139 April 1206 May 1089 June 994 July 1134 August 962 September 1087 October 1196 November 1258 December 1493