First Question: It is not clear to me if the residual is auto-correlated if the DW test statistic is above the upper critical value. Not quite clear in curriculum. I understand that the residual is not auto-correlated if the test statistic is below the critical value, and is auto-correlated if it is above. Second Question: It is not clear to me when to test for positive or negative auto-correlation. What DW test statistic do I use for negative auto-correlation? The curriculum only seems to refer to positive auto-correlation and does not distiguish between the two, as far as I can see at least. Many thanks for your help!

if DW > Upper Value we fail to reject Null of no serial correlation.