The point of testing is not to prove or disprove something. It’s to inform your judgment. People think they can use testing to prove whether navigation system “a” is better than “b” one. Wrong. Testing provides you with input which makes it easier to choose wisely - and with greater confidence - between “a” and “b.”
Don’t make me think
Being an expert in online usability Krug gathered his experience in a wonderful book. This summary of key thoughts will help you to remember most important principles and laws.