The Five Whys

Five Whys is “a ques­tion-ask­ing meth­od used to explore the cause/effect rela­tion­ships under­ly­ing a par­tic­u­lar prob­lem. Ulti­mately, the goal of apply­ing the 5 Whys meth­od is to determ­ine a root cause of a defect or prob­lem”. Developed by Taii­chi Ohno–one of the invent­ors of the Toyota Pro­duc­tion System–the oft-cited example is as fol­lows:

  • My car will not start. (the prob­lem)
  1. Why? – The bat­tery is dead. (first why)
  2. Why? – The altern­at­or is not func­tion­ing. (second why)
  3. Why? – The altern­at­or belt has broken. (third why)
  4. Why? – The altern­at­or belt was well bey­ond its use­ful ser­vice life and has nev­er been replaced. (fourth why)
  5. Why? – I have not been main­tain­ing my car accord­ing to the recom­men­ded ser­vice sched­ule. (fifth why, root cause)

I was intro­duced to Five Whys in a post by Joel Spol­sky back in early 2008 detail­ing their post-mortem exam­in­a­tion fol­low­ing a sys­tem out­age (which also looks at the prob­lems with SLAs).

Entre­pren­eur Eric Ries recently wrote a com­pre­hens­ive post detail­ing how to con­duct a Five Whys root cause ana­lys­is which I sup­pose acts as an update to this pre­vi­ous post of his where he intro­duces his read­ers to the Five Whys concept and adds this import­ant caveat:

The next step is this: you have to com­mit to make a pro­por­tion­al invest­ment in cor­rect­ive action at every level of the ana­lys­is.

Five Whys is a concept I’ve attemp­ted to–somewhat successfully–apply to myself and my devel­op­ment. When I make mis­takes or when I don’t under­stand some­thing I ask why until I find the root cause of my error, the mis­un­der­stand­ing, or the neg­at­ive reac­tion. Sim­il­arly, GigaOM’s Mike Speiser recom­mends Five Ways as one of the four tech­niques you should embrace in order to become at ease with ideas that make you uncom­fort­able.

You may find that your reac­tion is more about pro­tect­ing exist­ing ortho­doxy or the source of the idea than it is about the mer­its of the par­tic­u­lar approach at hand.

And of course, to end in a joke, you don’t want to ask why too many times (via Kot­tke).

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