Case Studies: Practical Applications of the 5 Whys

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Consider the following case studies to better understand how the 5 Whys technique can be applied in practice:

Case Study 1: Toyota Paint Defects
Toyota, where the 5 Whys technique originated, used this method to solve a persistent problem of paint defects in the Toyota production system.

Problem Statement: Cars were leaving the paint shop with minor imperfections that required costly overhauls.

1. Why were there stains on the cars?

because dust was settling on the wet paint

**2. Why did dust settle on the paint?

because the air in the paint shop was not clean enough

3. Why was the air not clean enough?

because the air filtration system was not working properly

**4. Why was the filtration system not effective?

because the filters were not changed regularly

**5. Why were the filters not changed regularly?

because there was no system to track the life of the filters and scheduled changes

Root Cause: Lack of a systematic approach to air filter maintenance in the paint shop.

Solution: Toyota implemented a regular filter change program and tracking system, significantly communication directors email lists reducing paint defects and rework costs.

Case Study 2: Analyzing Outages in the GitLab Database
In 2017, GitLab had to deal with a major database outage resulting in significant downtime and data loss.

Problem Statement: GitLab.com is down due to a database failure.

1. Why did GitLab.com go down?

because a directory was accidentally deleted from the production database

**2. Why was it deleted?

because a system administrator ran a command that deleted the data

**3. Why did the system administrator run that command?

They intended to eliminate replication lag by removing the database replica, but they missed the target.

**4. Why did they manage to delete the production database?

due to the lack of protective measures against accidental deletion of critical production data

**5. Why were there no safeguards?

because there were no internal approval-based controls to protect the production database from deletion

Root Cause: Insufficient operational safeguards and approval processes for critical database actions, combined with inadequate distinction between production and replication environments in the command interface.