For all the abuse that PHB gets from Dilbert, Alice, and others, I pity him. He is basically a naive and relatively dumb (but harmless manager) who gets riducule from all sides. True corporate thugs are a couple of layers above PHB. Scott Adam's CEO does not appear in the strip often enough.
Don't see why scott would distrust statistics. I always thought it was the people who create, use, and interpret statistics were the ones that couldn't be trusted. The statistics themselves are just data to be misinterpreted and exaggerated.
The best way for Dilbert to succeed in this situation is to have the PHB give the presentation. The PHB will have to respond to all questions with "I don't know, but I will find out and get back to you on that". Once the CEO forgets about the conversation, Dilbert is in the clear.