Lean Six Sigma Yellow Belt Certification Lean Six Sigma Yellow Belt Root Cause Analysis 1

Question 1

In the DMAIC methodology, during which phase is Root Cause Analysis primarily performed?

Accepted Answer

Analyze

Answer

Root Cause Analysis belongs in the Analyze phase, where teams examine collected data and use tools like fishbone diagrams and 5 Whys to identify the fundamental causes of defects before moving to solutions.

Question 2

What is the primary purpose of a Pareto chart when used in root cause analysis?

Accepted Answer

To identify the vital few causes responsible for the majority of defects

Answer

A Pareto chart applies the 80/20 rule, visually separating the 'vital few' causes (roughly 20%) that drive most problems (roughly 80%) from the 'trivial many,' helping teams prioritize where to focus RCA efforts.

Question 3

In a fishbone (Ishikawa) diagram, what do the diagonal 'bones' branching from the main spine represent?

Accepted Answer

Potential cause categories

Answer

The diagonal bones represent major cause categories (such as the 6Ms: Man, Machine, Method, Material, Measurement, Mother Nature). Sub-causes are then listed as smaller branches within each category.

Question 4

Which root cause analysis tool is best suited for visually determining whether a relationship exists between two process variables?

Accepted Answer

Scatter diagram

Answer

A scatter diagram plots pairs of data points for two variables on X and Y axes, making it possible to see whether a positive, negative, or no correlation exists — helping teams validate suspected cause-and-effect relationships.

Question 5

When applying the 5 Whys technique, what signals that you have reached a true root cause?

Accepted Answer

The answer points to an actionable process or system failure you can fix

Answer

The goal of 5 Whys is not to ask exactly five questions but to keep digging until you reach an actionable root cause — typically a process, system, or policy failure — where a countermeasure can be applied to prevent recurrence.

Lean Six Sigma Yellow Belt Certification Practice Test

Lean Six Sigma Yellow Belt Certification Practice Test

Lean Six Sigma Yellow Belt Certification Lean Six Sigma Yellow Belt Root Cause Analysis 1