5-WHY

Description:

The 5-WHY tool is used to find specific and systemic root causes of a problem. It is also used to find detection failure causes. It may be used several times in the MEASURE phase or in LEAN Manufacturing phase projects.

Objective:

Start with the problem and analyze it from a prevention and detection perspective and continue to ask WHY to each previous answer until the root cause is obtained. The tool name suggest that repeating this process five times can get to the root cause.

It can take greater or fewer questions and sometimes it may branch off in two or more directions. Keep drilling down until the real root cause(s) is found.

A review of Mistake Proofing is recommended prior to using the 5-WHY tool.

It’s goal is to do more than correct the obvious, but to dwell further into preventing it from happening again in the specific instance and systemically across a company, group of machines, operators, set of forms, etc.

It may take more or less than five questions, the point is to take this exercise seriously and ask the difficult question and get to the bottom of the problem. Only then can solid corrective actions for the immediate term and preventive actions for the long term be planned. It is more important to get the difficult, right solution than to run with the simple wrong.

This module is easy to explain but challenging to complete. It is key to gather all the inputs (x's) into your problem. These inputs to some degree are creating variation or moving the performance off the target. The quantification of this is done in the ANALYZE phase, first it is critical to obtain and document all of them.

The causes and root causes should also be linked into the Fishbone Diagram as the "bones" of the fish skeleton.

1) Assign ONE person to the corrective actions of each root cause.

2) Assign ONE person to the preventive actions of each root cause.

3) Agree on a specific completion date for each assignment.

4) Record all the names of the people involved in the exercise.

5) Record the date the exercise was completed.


This exercise should be done with those familiar and unfamiliar with the problem, 5-10 people. Those involved will present the most accurate review of the problem and those unfamiliar may have fresh perspectives for resolution.

Bottom Line!

This is similar to when attacking high RPN's in a FMEA, specifically the OCCURRENCE scoring component.

THEN, if it can not be prevented 100% of the time, go forward with the same agressive mindset to DETECT the problem 100% if the time if it does occur.

If the root cause can still pass through, attempt to reduce the severity of the failure mode or its impact to the project output.