Friday, February 6, 2009

Root Cause Analysis Using 5 Whys

My 4-year-old grandson was visiting recently and almost every sentence he spoke contained the word why. Why this and why that, he asked nonstop as only an inquisitive 4 year old can do.  As I patiently answered his questions, I was struck by how his constant questioning resembled the 5 Whys technique used in lean enterprise problem solving.  The 5 Whys is an extremely effective method used to getting to the root cause of the issue. 


The premise of the 5 Whys is very simple.  As the name implies, when conducting a root cause analysis you ask yourself and your team a series of 5 questions all beginning with the word why.  Each successive question builds on the previous answer.  Sounds simple.  In practice it is harder than you may think. 


To illustrate, suppose there was an issue involving tape on a packing carton coming loose.


  1. Why did the tape come loose on the packing carton?
    1. The tape was not applied with the necessary tension
  2. Why did the tape lack the necessary tension?
    1. The spring that applies the tension on the taper was loose.
  3. Why was the spring loose?
    1. The spring had been on the machine too long and had loosened due to wear.
  4. Why had the spring been on the machine to long?
    1. The spring had been on the machine to long because it was not replaced during preventive maintenance.
  5. Why was the spring not replaced as part of the preventive maintenance schedule?
    1. The preventative maintenance schedule only addressed the new model taping machines, which do not require use of a spring.


Solution: Update the preventative maintenance schedule and ensure that all items requiring preventative maintenance are scheduled.


While this sounds easy, it isn’t.  Your first several attempts will prove difficult and the tendency will be to stop before reaching the 5th Why.  I would urge you to press forward in an attempt to reach that 5th why and get to the true root cause of the issue.


Post Author: Royce Williard

copyright 2009, The Williard Group

1 comment:

  1. Mr. Willard,

    I used to work at Modus Media from 2000-2002 and remember you well and remember we spoke a few times. You mentioned Lean Six Sigma to me once and it was always in the back of my mind. About six months ago I began studying up on it and have been looking at the various tools in the LSS world. I was curious, are there any books that you would recommend that cover company profiles that have used LSS? I came across your blog and saw your Twitter feed as well.

    Matthew Randquist