Lean Six Sigma Yellow Belt Certification Statistical Thinking and Variation 2

Question 1

Control charts have control limits set at ±3 standard deviations from the mean because:

Accepted Answer

This range captures approximately 99.73% of common cause variation

Answer

Setting control limits at ±3 standard deviations captures 99.73% of natural process variation, making points outside the limits a strong signal of special causes.

Question 2

What is the key difference between control limits and specification limits?

Accepted Answer

Control limits are calculated from process data; specification limits are set by customer requirements

Answer

Control limits reflect what the process actually does (derived from data), while specification limits reflect what the customer requires — they measure entirely different things.

Question 3

A point falling outside the control limits on a control chart most likely indicates:

Accepted Answer

A special cause of variation has occurred

Answer

A point outside the control limits is a statistical signal that something unusual — a special (assignable) cause — has likely affected the process.

Question 4

A histogram is used in Six Sigma primarily to:

Accepted Answer

Display the frequency distribution of process data

Answer

A histogram displays how often values fall within defined intervals, revealing the distribution shape, central tendency, and spread of process data.

Question 5

What does a run chart help a Yellow Belt team identify?

Accepted Answer

Trends, shifts, or patterns in process data over time

Answer

A run chart plots data sequentially over time, helping teams detect non-random patterns such as trends, shifts, or cycles that may indicate special causes.

Lean Six Sigma Yellow Belt Certification Practice Test

Lean Six Sigma Yellow Belt Certification Practice Test

Lean Six Sigma Yellow Belt Certification Statistical Thinking and Variation 2