Quantifying usability
Jeff Sauro · interactions · 2006
"When you can measure what you are speaking about and express it in numbers, you know something about it. But when you cannot measure it, when you cannot express it in numbers, your knowledge is of an unsatisfactory kind: It may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of Science." ---Lord (William Thompson) Kelvin, pioneer in thermodynamics and electricity, 1891