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Lean toolkit / 02

Root Cause Analysis

Five Why with an evidence test on every link. A Why you cannot prove is a guess wearing a lab coat.

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Every Why must be provable with something you can point to at the process, not an opinion offered in a room. Tick the evidence box only when you have actually seen it.

Stop when the next Why leaves your control. If the chain dead-ends or branches, widen the search with the 6M fishbone below.

Problem statement — what, where, when, how much

Owner

Date

Containment in place

The chain

Each answer becomes the next question

Why 1Why does the problem occur?

Evidence seen at the processNot a theory offered in a meeting. What did you look at?

Why 2Why does that happen?

Evidence seen at the processNot a theory offered in a meeting. What did you look at?

Why 3Why does that happen?

Evidence seen at the processNot a theory offered in a meeting. What did you look at?

Why 4Why does that happen?

Evidence seen at the processNot a theory offered in a meeting. What did you look at?

Why 5Why does that happen?

Evidence seen at the processNot a theory offered in a meeting. What did you look at?

Fishbone — 6M

Use when the chain branches rather than runs

Man / people

Skill, staffing, training, handoff

Machine

Capability, wear, setup, tooling

Method

Standard work, sequence, decision rules

Material

Supplier, lot, spec, storage

Measurement

Gauge R&R, sample plan, definition

Environment

Layout, temperature, humidity, light, noise

Verified root cause and countermeasure

One countermeasure per verified cause

#

Root cause (verified)

Countermeasure

Owner

Effective

How the fix was proven — data, date, sample size

Where else this applies

Root Cause Analysis · DF Consulting · df-consulting.net · david@df-consulting.net

Working on something harder than a worksheet?

Tools do not fix processes. People with a method do.

I am David Fowles. I have spent 25 years in nuclear operations, power generation field service, manufacturing quality and supply chain, and I build the capability to keep an improvement after I leave. If one of these sheets has shown you something you would rather not solve alone, say so.

Email me See what I do

david@df-consulting.net
Connecticut, United States