5 Whys

The 5 Whys is a root-cause analysis technique in which you ask "why" repeatedly, usually three to five times, until you move past the symptoms of a problem to an underlying cause you can actually fix.

In depth

Developed by Sakichi Toyoda and popularized through the Toyota Production System, the 5 Whys starts from a clear, measurable problem statement (a defect, a line stop, a complaint) and asks "why did this happen?" of each successive answer. The analysis stops when it reaches an actionable cause (typically a missing step, control, or standard) rather than a dead end like "human error". Each answer must be based on evidence, and the resulting chain should read backwards with "therefore". It works best for single-track problems in quality, production, and maintenance; complex, multi-cause issues call for a fishbone diagram or a full 8D. In Azumuta, 5 Whys findings feed directly into CAPAs, so corrective and preventive actions get an owner, a due date, and verification.

See also

• 8D report
• CAPA

Azumuta resources

• Free 5 Whys root cause analysis template
• Kaizen in lean manufacturing