The question Why? on a cork notice board

A: They ask WHYs more than anything else.

“Honey, we need to go home. “


“Because it is dark.”


“Because it is night and the sun went home.”


“Because the sun was up whole day and was tired of shining down on the park. The sun needs to rest.”

“But, but… what about the moon? The moon is up. Why is it still dark?”

Toddlers are curious about the world and want to understand better what is going on around them. Problem solvers are curious about problems and want to understand what caused them.

Ask WHYs to identify the causes of a problem is one of the most critical part of RCA (Root Cause Analysis). The idea is to separate causal causes from root causes. When a root cause is removed from the sequence of the problem, the undesirable outcome is prevented from occurring. While a causal cause has an impact on the problem, removing it doesn’t prevent the recurrence of the problem.

Six Sigma uses the 5 WHYs technique in the Analyze phase of the Six Sigma DMAIC (Define, Measure, Analyze, Improve and Control). You keep asking WHYs until you identify the root cause of the problem and determine the relationship of the root causes of other problems.

The 5 WHYs technique is powerful because it is

·         Simple – doesn’t require any tool.

·         Effective – allows separating symptoms from causes easily.

·         Comprehensive – allows linking different problems, analyzing their root causes and their interactions.

·         Flexible – works alone or with other techniques.

·         Engaging – stimulates brainstorming and team work.

·         Inexpensive – just a team exercise.