The 5 whys method

A newsletter article. 

The method known as 5-Why or 5-Whys is an analysis method used to dig below the outward symptoms of a problem in order to find its real root cause.

The method involves asking "Why … ?" five times in succession.

This can sound deceptively simple.  It requires thought and intelligent application in order to find the right Why? questions to ask, as well as the discipline and persistence to follow the method.

The answer to one question leads you on to frame the next Why…? Question.  But it may not always be possible to ask or answer the next question immediately. You may need to gather and analyse more information in order to answer it properly, or do more thinking and brainstorming.

This method can be extremely valuable and powerful. It does require practice. But the more you use and apply it and the more you practice it, the more you'll begin to find the real underlying (root) causes of problems.

By the time you get to the fourth or fifth Why…? you are almost invariably looking straight at management practices as opposed to mere symptoms.

Example 1

Here is a real example from a training company.

Problem:  The wrong materials for training courses have been delivered to training venues on several occasions.

Why did it happen? The person packing and dispatching them for delivery made some mistakes. She was packing materials for three different courses at the time, was in a hurry and didn't notice. (Symptom)

Why was it overlooked?  She's quite new to the job and there hadn't been enough time for training. (Symptom)

Why was a new person doing this job without any apparent backup?  The person who used to do that job had left and everyone else was busy too. And there's nothing written down, such as a checklist of materials to pack, nor any procedure. (Symptom)

Why is there no procedure/guideline etc? We've just had so many new staff lately (turnover has been very high) that there's been no time for training or writing procedures. (Symptom)

Why is that? Root Causes: There is no effective training system in place. And no priority or importance has been placed on having some basic documentation in place: writing down essential information to make sure that things are done consistently, despite changes of personnel.

Note: It might also be worth while looking at why turnover is so high, and/or whether there is adequate advance planning occurring.

Example 2

Another real example, this time from a manufacturer of auto accessories:

Problem:  We can't keep Product XYZ in stock, although sales numbers haven't increased (ie, we're not selling any more of it).

Why can't we keep up? A: Our inventory is being used up to replace faulty products returned under warranty. (Symptom)

Why are the products returning?   A: There's a problem with the seal: it has to fit tightly into an indented rim. Sometimes the parts don't come off the line with quite enough tolerance to allow the seals to fit tightly enough, so it only shows up later when fitted to a vehicle. (Symptom)

Why is the fault happening?  A: Well, that tolerance is very fine and the castings we get sometimes don't allow quite enough depth for the very tight seal needed. Usually we pick up the problem at assembly and take it down a bit, but we don't always pick them all up. (Symptom)

Why don't the castings allow for the depth? A: The main body of the part is machined from castings we buy in, but the dimensions on the supplier's mould aren't quite accurate. It would cost more than $1200 to replace the mould, and Production is under strict instructions to save costs. (Symptom)

Why? Root Causes: Management doesn't understand or has not had communicated the impact that 'just save costs' is having on the casting/mould process or the engineering issues.  No one has identified that investing money on replacing the mould would save money spent on products replaced under warranty. It also sounds like the current quality system does not have an effective corrective action process that would identify why this particular product keeps being returned and why it keeps failing - and take effective action to prevent it happening again and again. 

Using the method

When attempting to solve a problem, a common error is to stop too soon when you're hunting down cause.  People keep taking the first or second simple answer, blinded by the symptoms or settling for the first 'apparent' cause. The first 'cause' offered is almost never the real root cause. And it's only when you find the real cause/s -- not just symptoms -- that you can take really effective action to remove the cause and prevent the problem cropping up again.

I've lost count of the times that 's/he made a mistake' or 'it was just human error' has been given as the supposed cause of a failure. Yes, of course we are human, and of course mistakes happen. But that's one of the reasons why good solid quality systems are needed - systems designed to have inbuilt controls and mechanisms that help avoid error in the first place.  And detect it if it does occur, then do something effective to stop it recurring.

Always look for the root cause, and beware of accepting too simple answers, or those immediate 'kneejerk' answers to questions. They're often misleading, and they may deal only with symptoms - the outward signs of a problem that are observed, but which are not its real root cause. One reason a good quality management system insists on a systematic approach to dealing with nonconformity, corrective and preventive action is because getting these right can produce quite enormous improvements in even smallish systems.

If you are responding individually to problems, weaknesses and failures, then you're almost certainly still in reactive mode: one of the hallmarks of an immature system. Organisations with mature, well-developed systems are proactive: they've already recognized the rich pickings to be had here, and use it to improve.

Aim to collect information on your problems and failures, analyse them and spend time on them. Because symptoms can crop up in various places and disguises, and fool you into thinking they are all different, whereas often they are often just 'more of the same'.

NB: The 5-Why method is closely related to the Cause & Effect (Fishbone) diagram; using them together can be very effective.

History:  Some people believe the 5-Why? Method was invented by Toyota. It's certainly something they've made extensive and effective use of, as well as other quality methods, as witness the reputation Toyota cars have for reliability. But the method itself has been around rather longer. The earliest known written version of the following rhyme which is often taught to British children is in John Gower's Confesio Amantis, approximately 1390 AD.

For want of a nail a shoe was lost,
for want of a shoe a horse was lost,
for want of a horse a rider was lost,
for want of a rider an army was lost,
for want of an army a battle was lost,
for want of a battle the war was lost,
for want of the war the kingdom was lost,
and all for the want of a little horseshoe nail.

Author:  Jane Bennett