[nwomack]

McDonalds quality control is second to none. Their standard menu tastes practically the same everywhere in the world. It's the same with Starbucks. I know that no matter what part of the planet I am at, I can get exactly what I expect to get. I'm never disappointed. I can't stress how important that part is. Bad quality control can really injure restaurants.

[mikeash]

Perfect consistency is only useful if your perfectly consistent product is any good. Much depends on your target audience. Bad quality control can hurt a lot, but so can perfect consistency in producing a bad product. If your audience is the sort that thinks McDonald's is quality food then that's obviously where you should aim, but many audiences don't.

[hessenwolf]

Having worked in Quality Control in a major multinational, and studied and lecture statistics, I have seen that significant decreases in quality are accepted in exchange for increased consistency.

[gaius]

Quality is the measure of how closely a finished product meets its design spec. McDonald's products are insanely high quality, despite not being very good - a Big Mac was never designed to be healthy and satisfying in the first place!

A relevant example of this is organizations who are CMM Level 5 certified.