Lean Sigma: A Practitioner’s Guide

7. Tools

01: 5 Whys

Overview

5 Whys is commonly listed more as a Lean tool than Six Sigma because it isn’t rigorously data-based, but it can be particularly useful, especially to Belts that get trapped in the minutia and don’t step back to see the bigger picture (see “Other Options”). The simple idea is to keep asking “Why” (usually five times) to ensure that the root cause(s) to the effects are fully understood. The reasoning is that the result of each time the Why is asked gives a different answer, in essence peeling back the onion as follows:

• First Why—Symptom
• Second Why—Excuse
• Third Why—Blame
• Fourth Why—Cause
• Fifth Why—Root Cause

A simple fictitious example demonstrates use of the tool well. A problem in London’s Trafalgar Square is that ...