CPP Statistical Process Control 2

Question 1

Which type of control chart is best suited for monitoring the number of defects per unit when the sample size varies?

Accepted Answer

u-chart

Answer

The u-chart tracks defects per unit and accommodates variable sample sizes, making it appropriate when inspection units differ in size.

Question 2

A process is said to be in a state of statistical control when:

Accepted Answer

Only common cause variation is present

Answer

Statistical control means the process exhibits only common cause (random) variation, with no special causes influencing the output.

Question 3

On an X-bar chart, what does the Western Electric Rule 2 (two of three points beyond 2 sigma) signal?

Accepted Answer

A potential shift in process mean requiring investigation

Answer

Two of three consecutive points beyond 2-sigma on the same side signals a probable shift in the process mean and should trigger investigation.

Question 4

What is the primary purpose of the R-chart used alongside an X-bar chart?

Accepted Answer

Monitor within-subgroup variation (spread)

Answer

The R-chart monitors variability within subgroups, ensuring the spread of the process remains stable alongside tracking the mean.

Question 5

A manufacturer samples 50 units each shift and records defective units. Which control chart is most appropriate?

Accepted Answer

np-chart

Answer

The np-chart is used for count of defective items with a constant sample size, making it ideal for this fixed-subgroup scenario.

(CPP) Certified Process Professional Practice Test