CQE Statistical Process Control

Question 1

What does a control chart's Upper Control Limit (UCL) represent in Statistical Process Control?

Accepted Answer

Three standard deviations above the process mean

Answer

The UCL is calculated as three standard deviations above the process mean, representing the upper boundary of natural process variation.

Question 2

Which control chart is most appropriate for monitoring the number of defects per unit when the sample size varies?

Accepted Answer

u-chart

Answer

The u-chart monitors the average number of defects per unit and accommodates variable sample sizes, making it ideal when inspection units differ in size.

Question 3

A process capability index (Cpk) of 1.33 indicates the process is:

Accepted Answer

Capable with a safety margin

Answer

A Cpk of 1.33 corresponds to a 4-sigma process, meaning the process is capable with a reasonable safety margin beyond the minimum threshold of 1.0.

Question 4

What is the primary purpose of a Western Electric (WECO) rule in SPC?

Accepted Answer

To detect non-random patterns indicating a special cause

Answer

WECO rules are supplementary run rules applied to control charts to detect non-random patterns that signal special cause variation beyond just points outside control limits.

Question 5

In an X-bar and R chart, which component measures within-subgroup variation?

Accepted Answer

R chart

Answer

The R (Range) chart tracks the within-subgroup variation by plotting the range of each subgroup, while the X-bar chart tracks between-subgroup variation.

CQE - Certified Quality Engineer Practice Test

CQE - Certified Quality Engineer Practice Test

CQE Statistical Process Control