  Given an Orthogonal Array we analyze the aberrations of the sub-fractions
which are obtained by the deletion of some of its points. We provide formulae
to compute the Generalized Word-Length Pattern of any sub-fraction. In the case
of the deletion of one single point, we provide a simple methodology to find
which the best sub-fractions are according to the Generalized Minimum
Aberration criterion. We also study the effect of the deletion of 1, 2 or 3
points on some examples. The methodology does not put any restriction on the
number of levels of each factor. It follows that any mixed level Orthogonal
Array can be considered.
