An appellant's chance for reversal in an ex parte appeal are around 30%. One reason for this relatively constant reversal rate is that the Board often seems to give the benefit of the doubt to the Examiner in some areas, including inferring how an Examiner may be relying on the cited references. It is rare to see the Board call out an Examiner for making nonsensical and unsupported assertions to a level that fails to give the applicant proper notice.
One example of this rare instance is in SN 13/490,885 which relates to a General Motors invention involving an engine control system. GM appealed numerous rejections that were, even giving the Office the benefit of the doubt, poorly founded and poorly explained. After calling out several of the Examiners' unfounded statements, the Board noted that:
A rejection must be set forth in sufficiently articulate and informative manner as to meet the notice requirement of 35U.S.C. §132, such as by identifying where or how each limitation of the rejected claims is met by the prior art references. (citations omitted). It is neither our place, nor Appellants ’burden, to speculate as to the basis for rejecting claims. (citations omitted).
So, if you have rejections that are so poorly founded and explained that it is not possible to discern the basis of the rejection, consider raising this issue in your appeal. The Administrative Procedure Act requires a clear record and the statute requires that the Office give the applicant notice of the grounds of rejection. It is thus the PTO's obligation to provide timely notice to the applicant of all matters of fact and law asserted, and if it fails to do so that can be sufficient grounds for reversal.