Project Toolkitby Maxime Lab
Scope and Quality · tool 3 of 9

Scope and Quality · tool 3 of 9

5 Whys & Fishbone

5 Whys & Fishbone: solves a problem at its source instead of repeatedly fixing the symptoms.

Best for: Recurring issues, incidents · Time: 30–60 minutes
Domain: Scope · Focus area: Monitoring and Controlling

Problem
Release shipped 3 days late
Why 1
Testing started late
Why 2
Test environment wasn’t ready
Why 3
Environment request was sent late
Why 4
Nobody owned environment set-up ← root cause
Fix: add “environment set-up” to the WBS and the RACI with a named owner.

How it works

The 5 Whys asks “why?” about five times, each answer becoming the next question, until you reach a process cause you can fix. For complex problems, the Fishbone (Ishikawa) diagram first maps possible causes along bones: People, Process, Tools, Materials, Environment, Measurement.

  • Start from a fact, not an opinion.
  • Stop when the answer is a process you can change.
  • Look for causes in processes, not culprits.

How to apply it

  1. Write the problem as a measurable fact: “Release 2.1 shipped 3 days late”.
  2. For a simple issue, chain the whys with the people involved.
  3. For a complex one, draw the fishbone, brainstorm causes per bone, then run 5 Whys on the most likely ones.
  4. Define one corrective action with an owner and a date.
  5. A few weeks later, check that the problem hasn’t come back.
Pro tip

If your last “why” ends with a person’s name, keep going. Ask why the process let that happen.

Quick check

Your last “why” ends with a person’s name. What do you do?

Sources

  • PMBOK® Guide, 8th edition, and The Standard for Project Management (PMI, 2025)
  • T. Ohno, Toyota Production System

Last reviewed 2026-11-02 against the PMBOK® Guide, 8th edition · Practitioner review pending · How this guide is made