The Durbin-Watson
statistics can be used to test for a correlation (non-randomness) of the residuals
[231],[234],[235].
The null hypothesis that there is no correlation between the successive residuals
is evaluated by:
(26)
Thereby
ei is the residual
corresponding to the observation i
and ei-1 is the residual
of the preceding observation. The d
value is compared to the lower and upper critical values dL and dU proposed by Durbin and Watson
[236].
If the calculated d is smaller
than the tabulated lower critical value dL,
the null hypothesis is rejected meaning that the residuals are correlated. If
the calculated d is bigger than
the tabulated upper critical value dU,
the correlation of the residuals is negligible and if the calculated d is between both tabulated critical values,
the test is inconclusive.