5-whys

From Lean-Agile

This is an excerpt from Lean-Agile Software Development: Achieving Enterprise and Team Agility. In particular, the chapter An Agile Developer's Guide to Lean Software Development.

For root cause analysis, it is common in Lean to use the “Five Whys.” This technique, credited to Sakichi Toyoda, the founder of Toyota Industries, involves asking why something happened and then why that happened and then why that happened, continuously exploring the cause and effect relationships underlying a particular problem until you have drilled down to the root cause.