Simplified Durbin-Watson Test

Draper and Smith (1998) suggest that, in many practical situations, one can work as if Dl does not exist and, therefore, consider only the Du value. This is 

There is no easy answer as to how reliable the simplified test is, but the author of this chapter finds that the Draper and Smith simplified test works well. However, generally, the researcher is urged to check out the model in depth to be sure a process problem is not occurring or some extra unaccountable variable has been included. 

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