5-Why is a problem solving exercise that helps us get to the root cause. The approach is to keep asking why until the root cause is arrived at.

The number five is a general guideline for the number of Why’s required to reach the root cause level, but asking “Why?” five times versus three, four, or six times is not a rigid requirement.


Here is a root cause analysis exercise that only required three Why’s

In this example only three of the five why’s were needed. See how addressing the first two why’s produces little value?

5-Why Moves us From Symptom to Cause

The 5-Why thought process guides us to lasting corrective actions, because we address root causes and not symptoms. Let’s look at the effects of addressing the 1st Why versus the 5th Why in the above exercise –

Note the corrective action effectiveness as each deeper Why is addressed above:

  • Responding to the first Why is almost counterproductive:  we are retraining the stock pickers in our warehouse, because we assume that they pulled the wrong item from our inventory.  In reality, the stock pickers performed their jobs perfectly, and the real cause was mislabeled parts coming from the supplier.
  • Addressing the second Why (having the supplier check their stock for other mis-labeled products), but this action will only contain the current the problem short-term.
  • Addressing the third why is the way to go in this case, because it focuses on the cause:  mistakes being made in the label application process.

Companies routinely address systemic causes like the 5th “Why?” above, eliminating reactionary problem solving and shifting resources to prevention activities over the long run.

Reporting Format

The above example shows a typical 5-Why format for narrow problem statements where one cause-path exists.  For broader problem statements where two or more causes are involved, the following format is effective –

5-Why format for multiple causes

This format is also very useful for explaining the causes behind the top bars on a Pareto chart, as in the case above where a team has collected data and built a Pareto chart on top-level reasons for downtime.  Instead of simply showing a Pareto chart with no further insight into each Pareto bar, the team selects the top two items (material shortages and downtime on machine ABC) and uses the 5-Why format to explore the root causes of each.

Noting Actions Directly on the Document

Remember that 5-Why exercises are only useful when actions come from the meeting.   Take time to document those actions/next steps with the team, and then follow up to ensure that they are implemented.  Recording action items to the 5-Why document itself is a great practice, as shown below.  Don’t forget to agree on the action owners and estimated timing!

5-Why format with corrective actions noted

Leading a Root Cause Analysis Meeting

1.  Schedule the Meeting

Schedule a time for the 5-Why discussion, and invite individuals who know about the product and/or process at hand.  Your goal should be to run an efficient meeting and complete the 5-why in one session, no more than an hour long.   5-Why is not meant to be a lengthy exercise.

2.  Plan for a Successful Outcome

Clearly state the problem and desired outcome in advance of the meeting, via the meeting notice, email, etc..  An example of this would be:  “Complete a 5-Why analysis on problem ABC and understand next steps for further investigation / corrective action.” Have an easel pad or large dry-erase board in the meeting room, and have the problem statement and 5 Why column headers already documented before the attendees show up.

3.  Run a Successful Meeting

Remember that the success of your meeting will determine attendance at your future meetings!  You want to have a reputation for holding productive meetings, being highly respectful of attendees while keeping the meeting on track to achieve desired outcomes.

Take a couple of minutes at the start of the meeting and explain that 5-Why is a way to document root causes, showing an example (use the Powerpoint file above if you don’t have a more relevant example from your company).

Take another couple of minutes to clearly state the problem, and make sure everyone agrees with the problem statement.  The more specific the problem statement, the better.

See the our video on this page for handling the 5-Why discussion itself – there are a few important points that will help you manage the discussion in the meeting.

4. Agree on Follow-Up Actions / Next Steps

Take time to document those actions/next steps with the team, and then follow up to ensure those actions are implemented.


5-Why is useful for straightforward problems with systemic causes like the case noted above, where poor preventive maintenance is the systemic cause for unplanned equipment downtime.

In cases when the root cause is not readily apparent, 5-Why by itself will not solve the problem.

For example, if a toy manufacturer needs to improve color consistency in a product, they will need to understand which factors influence color the most (otherwise they might not need a Six Sigma project to begin with).  In cases like this, structured analysis methods like multi-vari, correlation analysis, and DOE may be necessary to actually learn the physical relationships between the input variables (process settings, raw materials, etc.) and output variables (in this case, color).  If your team is attacking a number of product variation challenges, then read Keki Bhote’s World Class Quality for a highly effective approach.