Ask any student of engineering, the answser is all in the metrics. If you cannot 'nail it' to a number, then you're just doing a magic show. Lots of idioms are made up about this: 'experience', 'the quality process', ...
This presentation opens with a fabulous title, illustrates their process openly, and prescribes a wonderful future.
Great publication for a top quality (and reproduceable) home-brewing future!
The future begins now.