Statistical Process Control Flashcards
6 cards from real CQE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Statistical Process Control flashcards as text
What does a control chart's Upper Control Limit (UCL) represent in Statistical Process Control?
Answer: Three standard deviations above the process mean
The UCL is calculated as three standard deviations above the process mean, representing the upper boundary of natural process variation.
Which control chart is most appropriate for monitoring the number of defects per unit when the sample size varies?
Answer: u-chart
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.
A process capability index (Cpk) of 1.33 indicates the process is:
Answer: Capable with a safety margin
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.
What is the primary purpose of a Western Electric (WECO) rule in SPC?
Answer: To detect non-random patterns indicating a special cause
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.
In an X-bar and R chart, which component measures within-subgroup variation?
Answer: R chart
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.
A process with Cp = 1.5 but Cpk = 0.8 tells you that the process is:
Answer: Highly capable but significantly off-center
A high Cp with a low Cpk indicates the process spread is small enough to meet specs but the process mean is shifted significantly off target.