Online 5-Why Analysis Tool

Find the Root Cause of a nonconformity in 3 directions: Occurrence, Detection, and System.

5-Why Analysis

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Problem Statement:
A. Why did the defect OCCUR? (Occurrence)
Who: Deadline:
B. Why was it NOT DETECTED? (Detection)
Who: Deadline:
C. Why did the SYSTEM FAIL? (System)
Who: Deadline:
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Author: Pavel Ryvola | Updated:

What is the 5-Why Analysis Method?

5-Why Analysis is a fundamental quality management tool for Root Cause Analysis (RCA). The method consists of repeatedly asking the question "Why?" to drill down into the previous answer. The goal is not to find human error, but to uncover hidden process or system failures. The rule of "five" is just a guideline – sometimes three iterations are enough to find the actual root cause, other times it takes seven.

When and why should you use 5-Why Analysis?

  • Customer Claims (8D Report): A standard requirement for developing steps D4 (root cause analysis) and D6 (corrective actions).
  • Automotive Standards: The tool is fully compatible with and required by IATF 16949, VDA methodologies, and ISO 9001.
  • Process Improvement (Lean Management): Quick identification of waste (Muda) and process failures.

Practical Example: Why did the machine stop?

1. Why did the machine stop? (Because a fuse blew.)
2. Why did the fuse blow? (Because a bearing seized.)
3. Why did the bearing seize? (Because it wasn't sufficiently lubricated.)
4. Why wasn't it lubricated? (Because the oil pump isn't working.)
5. Why isn't the pump working? (Because the maintenance system doesn't prescribe its regular maintenance. <- Root Cause!)

What is a 3-Legged 5-Why Analysis?

Modern manufacturers and OEMs require an advanced form of this method. The problem is not broken down in just one path; root causes are investigated in 3 independent directions simultaneously:

Leg Question Goal Root Cause Example
1. Occurrence Why did the error physically occur during production? Excessively worn tooling.
2. Detection Why did the inspection fail to catch the defect before shipping? Camera sensor out of tolerance.
3. System Why did our QMS allow this situation to occur? Error in the PFMEA process, missing TPM maintenance.

What's next?

The 5-Why analysis is strongest in combination with broader brainstorming. If you get stuck, first create an Ishikawa diagram, which will show you all possible directions. Once you find the root cause using 5-Why and implement Corrective Actions, insert the results directly into our online 8D Report for sharing with customers or management.

Top Defect

The 5-Why method is a root cause analysis technique. It involves asking "Why did this happen?" and then asking "Why?" again to the answer. By repeating this, we reach the systemic cause of the problem.

A 3-Legged 5-Why examines a problem from three independent perspectives: 1. Why the defect occurred, 2. Why it wasn't detected, and 3. Why the system failed.