Original subtitles

- Hi.

I'm William Lidwell, and this is

Universal Principles of Design.

In this movie a root cause for want of a nail.

For want of a nail a shoe was lost.

For want of the shoe, a horse was lost.

For want of the horse, a knight was lost.

For want of the knight, a battle was lost.

For want of the battle, a kingdom was lost, and all

for want of a nail.

This proverb, which dates back to at least

the 14th Century, exemplifies the foremost

challenge of design, that is, developing

a deep understanding of problems.

The temptation, in fact the human tendency,

is to presume that problems have single,

proximal causes, the cause immediately

preceding the problem.

The kingdom was lost because the battle

was lost, and that's it.

That is how news is typically reported,

how history is typically written, and how

courses are typically taught, but this

is rarely the case in reality.

The kingdom was lost due to a paucity of nails.

That is the deeper truth in the proverb,

the root cause.

But, of course, even this is over simple.

Was there a shortage of iron that led to

the shortage of nails?

Perhaps the shortage was due to bad

inventory management, or perhaps,

an incompetent apprentice.

All of these factors and more could have

played a part in the loss of the kingdom.

So, the challenge is to understand the causal

chain that led to the observed problem,

identify the key links in that chain and how

they relate to one another, and then target

those areas where we have the most leverage

to make a significant impact.

The goal of this lecture is to give you a tool to

figure out how to ask the right question, to

understand problems deeply.

That tool is called Root Cause Analysis.

Root Cause Analysis is a way of understanding

problems in terms of their causes, with the

goal of finding the first event that caused

everything else.

The notion is that everything after the root cause

is a symptom or an aftereffect, and treating

symptoms won't cure the disease.

So, what is a root cause?

A root cause is defined as the key initiating

cause in a sequence of events that leads to

a problem event.

Most problems, especially difficult problems,

have multiple causes, and their proximal causes

are rarely their root causes.

Now, there are a bunch of different ways to do

root cause analysis.

We're going to focus on a technique called

"The Five Whys," that is, asking why an event

occurred, five causes deep, plus or minus.

This technique was developed in the 1930's by

Sakichi Toyoda, the acclaimed inventor and founder

of Toyota Industries Corporation, which would

later become Toyota Motor Corporation.

The Five Whys remains a key part of problem solving

training for Toyota employees to this day,

not to mention designers, engineers and managers

throughout the world.

An example of how it works.

Why did the welder burn herself?

She wasn't wearing protective clothing.

Why wasn't she wearing protective clothing?

It was hot in the room.

Why was it so hot?

The air conditioner was broken.

The root cause of the accident was a

broken air conditioner.

This is not to say that you don't address other

problems in a causal chain.

For example, perhaps the welder needed better

safety training.

But, you focus on the root cause, fixing

the broken air conditioner.

One more example.

During a visit to one of Amazon's Fulfillment Centers

in 2004, Amazon CEO Jeff Bezos learned

about an accident in which a worker injured his finger.

He reportedly walked to the whiteboard and started

asking the group questions in the manner of Five Whys.

Why did the worker damage his thumb?

The team replied, "because his thumb got caught

in the conveyor."

Why did his thumb get caught in the conveyor?

The team said, "because he was chasing his bag,

which was on a running conveyor."

Why did he chase his bag?

The team said, "because he had placed his bag

on the conveyor, which then started unexpectedly."

Why was his bag on the conveyor?

The team replied, "because he was using the conveyor

as a table."

Ah ha.

Bezos and team concluded that the root cause

of the accident was really the lack of a surface

on which associates could lay their belongings.

The solution was to add tables to the work stations,

which is what they did.

So, whether you use your understanding of

root causes and the Five Whys technique to

identify and solve the right problem, or to

more deeply understand problems and identify

the causal links where you have the most leverage,

remember the kingdom was lost for want of a nail.