5 Why Analysis
Drill down to root cause by asking "why" iteratively
What is 5 Why Analysis?
The 5-Why Analysis is a root cause investigation technique that works by repeatedly asking "Why?" until you reach a cause the team can act on. Starting from a known problem or symptom, each "why" peels back a layer. You rarely need exactly five — sometimes three are enough, sometimes seven are needed. The rule is: stop when you reach a cause that is actionable and within the team's control.
When to Use It
- •After the fishbone diagram identifies the top 2-3 suspected root causes
- •When a problem keeps recurring despite previous fixes — the real root cause has not been found
- •When the team needs a fast, structured way to investigate a specific cause without extensive data collection
How to Use It: Step by Step
- 1
State the problem clearly
Write the specific symptom or cause from the fishbone at the top. Be precise: "Claims are rejected" is too vague. "8.3% of claims are rejected due to member ID mismatch" is actionable.
- 2
Ask "Why does this happen?"
Write the answer. It should be a factual statement, not an opinion. If there are multiple answers, branch the analysis.
- 3
Repeat for each answer
Ask "Why?" again for each response. Continue until the answer is a systemic cause that the team can address with a process change, policy update, training, or system fix.
- 4
Verify with data
The final root cause should be verifiable. Ask: "If we fix this, will the original problem go away?" If not, continue asking why.
Example
Payment postings crash twice per day
Why do payment postings crash? Because the batch job exceeds the memory limit. Why does it exceed the memory limit? Because the batch includes all records, not just new ones. Why does it include all records? Because the query has no date filter. Why is there no date filter? Because the original developer assumed the table would stay small. Root cause: The batch query was never optimized for growth. Fix: Add a date filter and optimize the query for incremental processing.
Pro Tips
- ✓Branch when there are multiple valid answers to a "Why?" — do not force a single chain
- ✓Stop asking when you reach something the team can change — do not drill into causes outside your control
- ✓Watch for circular logic: if Why #4 sounds like Why #1, you have gone in a circle
- ✓Document the chain visually — it becomes a powerful communication tool for stakeholders
Facilitation Guide
Run a 90-minute root cause workshop. Begin by reviewing the problem statement from Step 1 (5 min). Draw the fishbone skeleton on a whiteboard and have each person write causes on sticky notes in silence (15 min). Place and cluster notes on the fishbone, discussing as a group (25 min). Vote on the top 3 root causes using dot voting (10 min). Run 5-Why drills on the top 3 causes (25 min). Summarize findings and validate with available data (10 min).
Other Tools in Step 2
Fishbone Diagram
Cause-and-effect analysis using the 6M framework: Man (People), Machine (Equipment), Method (Process), Material (Inputs), Measurement (Metrics), Mother Nature (Environment)
Force Field Analysis
Map driving forces vs. restraining forces for change
Check Sheet
Structured tally sheet to collect and quantify data by category over time periods
Pareto Analysis
Rank causes by frequency or impact to identify the vital few (80/20 rule)
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