The “5-Whys” is a simple technique used in the “Analyze” phase of the Six Sigma DMAIC methodology (Define, Measure, Analyze, Improve, Control). By repeatedly asking the question “why” symptom layers are systematically peeled away, leading more directly to the root cause(s) of a problem. It may also illuminate inter-relationships between different root causes.
The 5-Step “5-Whys” Process
1. Write down the specific problem to help describe it more fully. This also enhances team focus (i.e., to ensure everyone is working together to solve the same problem).
2. Ask why the problem occurs and write the answer(s) down below the problem.
3. Use the answer(s) from step #2 to frame the next “why” question.
4. If this/these answer/s fail(s) to identify the root cause of the problem, ask “why” again, and record the answer(s).
5. Repeat this loop until the problem’s root cause(s) is/are identified. It may take a lesser or a greater quantity of “why”s than 5 to determine the root cause. Five is merely typical.
Simple Example to Illustrate the Process
Problem Statement: The firm’s largest customer is regularly receiving products that don’t meet their specifications. (They’re mad at the salesperson and are threatening to find a new supplier.)
1. Why is this customer being shipped products that don’t meet their specifications?
Because “Manufacturing” is building the products to a specification that is different from what the customer and the salesperson agreed to.
2. Why is “Manufacturing” building products to a different specification than what the customer and the salesperson agree to?
Because “Manufacturing” does not precisely fulfill the original purchase order specifications.
3. Why doesn’t “Manufacturing” fulfill the original purchase order specifications?
Because “Manufacturing’s” finished products correctly reflect their work orders, but these work orders do not match the customer’s original purchase order specifications.
4. Why don’t the original purchase order spec’s and the manufacturing work orders match?
Because the manufacturing work orders are completed by the Manufacturing Director (or one of his people) based on specifications verbally relayed from the Director of Sales.
5. Why does the Director of Sales verbally relay customer specifications from the purchase orders instead of following the established procedure (i.e., written purchase order electronically submitted by the salesperson to Director of Sales who electronically signs/forwards same to the Director of Manufacturing)?
Because the Director of Sales doesn’t read/reply to e-mails, etc. in a timely manner but nearly always answers his phone. He says “I don’t trust computers”. Consequently, the salesperson calls in the purchase order information and mostly completes the correct form later. To keep things moving the Director of Sales relays what the salesperson called in. He does this by phone or by walking over to talk with the Director of Manufacturing. In this case … exactly 5 “Whys” were required to discover the root cause of the problem: The Salesperson and the Director of Sales are both violating established procedure, and “Manufacturing” is complicit by not requiring the procedure to be followed.