An extension of the topic on identifying root causes using a 5 Whys approach that will lead toward building a data collection plan (DCP).

1. Section & Lesson #:
Pre-Requisite Lessons:
Complex Tools + Clear Teaching = Powerful Results
Identify Root Causes – 5 Whys
Six Sigma-Measure – Lesson 24
An extension of the topic on identifying root causes using a 5 Whys
approach that will lead toward building a data collection plan (DCP).
Six Sigma-Measure #23 – Identify Root Causes – C&E Diagram
Copyright © 2011-2019 by Matthew J. Hansen. All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted by any means
(electronic, mechanical, photographic, photocopying, recording or otherwise) without prior permission in writing by the author and/or publisher.

2. Why Do We Need This Tool?
o Remember, our goal of building the transfer function (Y = f(X)) begins with the DCP.
• We should already know the Y, so now we need to find the potential X’s for the transfer function.
• The data collection plan (DCP) helps ensure we have enough data measuring the Y and every X.
• Below is the method previously described for helping to build the DCP:
Copyright © 2011-2019 by Matthew J. Hansen. All Rights Reserved. No part of this publication may be
reproduced, stored in a retrieval system, or transmitted by any means (electronic, mechanical, photographic,
photocopying, recording or otherwise) without prior permission in writing by the author and/or publisher.
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1. Define phase
items plus Y &
defect definitions
2. Validate Y &
defect definition
with Team
3. Identify
potential X’s
4. Narrow
down to most
critical X’s
5. Build a data
collection plan
for critical X’s
INPUT to Meeting PROCESS during Meeting OUTPUT from Meeting
Tools: Cause & Effect (C&E) Diagram (a.k.a.,
Fishbone/Ishikawa diagram) and 5 Whys
Tools: Cause &
Effect (C&E) Matrix
Tools: Sample Size Calculator
& Data Collection Plan

3. 5 Whys Defined
o What is 5 Whys?
• It’s a method of asking “Why?” about 5 times for each cause to drill down to the potential root
cause. It doesn’t have to be 5 questions if the team believes they drilled to a reasonable depth.
o Below is an example of 5 Whys:
• In the 1960’s, Washington DC officials in charge of the Jefferson Memorial feared Jefferson’s statue would be
damaged by constantly washing off bird droppings. Their plan was to encase the statue in a thick layer of plastic
costing $300K for the encasement and $20K/yr to maintain it. A GAO auditor came to ask “why”.
• The auditor bought a $2 solenoid to delay the lights until 30 minutes after dark. The flies were attracted to
other light sources so the spiders and birds left and it was no longer necessary to encase the statue.
Lean and Six Sigma Workshop (Created by Matt Hansen) 3
Why encase the
statue in plastic?
Because the constant cleaning of
the statue will quickly deteriorate it
Why does it need
cleaning so often?
Why are so many
birds in here?
Why are so many
spiders in here?
Why are so many
flies in here?
Because the birds in here
leave droppings on it.
Because they’re attracted
to all the spiders in here.
Because they’re after the flies
coming at night from the tidal basin.
Because they’re attracted to the lights
illuminating the memorial at night.

4. Practical Application
o Identify a prior project or initiative you worked in your organization.
• Try using the 5 Whys approach for that project or initiative by answering the following:
 What was used as the critical metric (project Y)?
 How would you define a defect?
– This would be the ultimate “effect” for which you’re trying to find a cause.
 Why did the organization experience that effect?
 Continue asking a series of “Why” questions until you reach a reasonable level that could represent the
root cause for that undesirable effect.
Copyright © 2011-2019 by Matthew J. Hansen. All Rights Reserved. No part of this publication may be
reproduced, stored in a retrieval system, or transmitted by any means (electronic, mechanical, photographic,
photocopying, recording or otherwise) without prior permission in writing by the author and/or publisher.
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