Plumb-Ace advertises that its plumbers are more qualified than plumbers at any other major plumbing firm in the region because Plumb-Ace plumbers must complete a very difficult certification process
Plumb-Ace plumbers may or may not be more qualified, but clearly the certification process is not very difficult, because nearly everyone who takes the written portion of the certification exam passes it very easily
presumes that since one part of a whole lacks a certain characteristic, the whole must lack that characteristic as well