Root Cause & Waste Notes

Take one problem that keeps coming back, trace it to causes you can test, find the waste in the process around it and price the biggest pieces. You finish with one cause you have checked, not the first explanation that sounded right.

Evidence: the 5 Whys and the fishbone diagram are practitioner tools; the 5 Whys is contested as a way to find causes in complex problems (weak or contested). The waste categories come from Toyota and lean practice (mixed evidence). Force field analysis is a practitioner thinking aid. Treat every output of this page as a hypothesis until Step 3.

Use it when:

• A problem returns after you thought it was fixed, and fixes so far have treated symptoms.
• You are about to design a better process and need to know what you are really fixing.
• You want a cost on rework, waiting or duplicated work before you ask for time or money.

Skip it when:

• You have not yet mapped how the work flows today: start with 8.1 Process Map (Current State).
• You already know the cause and need a design: go to 8.8 Future-State Process Sketch.

The tools here share one claim: the problem you can see is rarely the problem you have, and structure beats intuition when you dig for causes. Their evidence is thinner than their fame. The whys chain comes from Toyota practice (Ohno, 1988). The patient safety literature warns that, for complex problems, single root causes are rare and a tidy chain can create false confidence (Card, 2017). The fishbone diagram (Ishikawa, 1976) is an untested way to spread attention across cause categories, and root cause analysis as a whole draws similar criticism (Peerally et al., 2017). The waste categories have a large but mixed applied literature (Ohno, 1988; Womack & Jones, 1996).

So use them to generate hypotheses, then test. Let the chain end where it ends and expect several unequal causes. Use the fishbone to correct the room's bias: a crowded People branch beside an empty Measurement branch describes who attended, not what happened. Name waste in the process, not in persons.

Describe what happens, how often and what it costs. A symptom with a number beats a feeling.

Strong answer: (illustrative numbers) "Roughly 1 in 6 kitchen orders is delivered with a wrong or missing part, about 4 a month, each costing a second trip and a day of the fitter's time." Not: "Quality is poor."

Illustrative example: the company and all numbers are made up.

The operations manager of a kitchen joinery near Gothenburg sees wrong or missing parts on about 1 in 6 deliveries. She runs the session with a planner, a workshop foreman and a fitter, not alone.

Step 2: the whys chain runs: wrong part delivered, parts list differs from the drawing, list copied by hand from the quote, quote changed after the list was made, no one told the planner. It ends on a process fact. The fishbone confirms it under Process and Measurement (changes are not logged), while People has only "stress", which the group agrees is a result, not a cause.

Step 3: the group expects errors to cluster in orders changed after quoting. A look at the last 30 errors shows most were changed orders. The test: one team gets a change notice to the planner for four weeks.

Step 4: the largest waste is rework trips, priced at about 4 a month × 2 hours × 2 people.

Step 5: next step, owner "operations manager", date "Friday week 3": start the change notice; measure again after four weeks.