Five Whys

Toyota’s ‘Five Whys’ process is well known to engineers: it’s one of the basic problem-solving tools in modern engineering management systems like Six Sigma and Total Quality Management. Here’s how Taiichi Ohno introduces the process in Toyota Production System: Beyond Large-Scale Production (1978):

When confronted with a problem, have you ever stopped and asked why five times? ( It is difficult to do even though it sounds easy. )