CPP Statistical Process Control 3

Question 1

Process capability index Cp measures:

Accepted Answer

The ratio of specification width to process spread

Answer

Cp compares the total specification width (USL − LSL) to the process spread (6 sigma), indicating whether the process fits within tolerances.

Question 2

A process has a Cp of 1.5 but a Cpk of 0.8. What does this indicate?

Accepted Answer

The process spread fits specs but it is not centered

Answer

A high Cp with a low Cpk means the process spread is narrow enough but the process mean is off-center, pushing output toward one specification limit.

Question 3

Which SPC chart would you use to monitor the time between failures in a low-defect manufacturing environment?

Accepted Answer

g-chart

Answer

The g-chart (geometric chart) monitors the number of events or time between rare occurrences, suitable for very low defect rate processes.

Question 4

Common cause variation in a process is best addressed by:

Accepted Answer

Fundamentally redesigning or improving the process system

Answer

Common causes are inherent to the system and can only be reduced through systematic process improvement or redesign, not by reacting to individual points.

Question 5

What is the effect of increasing subgroup size (n) on the control limits of an X-bar chart?

Accepted Answer

Control limits narrow, making the chart more sensitive

Answer

Larger subgroup sizes reduce the standard error of the mean, narrowing control limits and making the chart more sensitive to process shifts.

(CPP) Certified Process Professional Practice Test

(CPP) Certified Process Professional Practice Test

CPP Statistical Process Control 3