SPC Fundamentals 2

Question 1

Which of the following best describes 'common cause variation' in a process?

Accepted Answer

Variation inherent to the process that is always present

Answer

Common cause variation is the natural, inherent variability in a process that is always present and results from many small, everyday factors.

Question 2

On an X-bar chart, what does a single point beyond the upper or lower control limit indicate?

Accepted Answer

A potential special cause that should be investigated

Answer

A point beyond a control limit is a signal of special cause variation that warrants immediate investigation.

Question 3

What is the primary purpose of a process capability index (Cp)?

Accepted Answer

To compare the process spread to the specification width

Answer

Cp compares the specification width (USL − LSL) to the process spread (6σ) to indicate whether the process can fit within specifications.

Question 4

A rational subgroup in SPC is best defined as a group of measurements that:

Accepted Answer

Minimizes the chance of special causes occurring within the group

Answer

Rational subgroups are sampled so that variation within the group reflects only common causes, making between-group variation a reliable signal of process changes.

Question 5

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

Accepted Answer

u chart

Answer

The u chart monitors the average number of defects per unit and accommodates varying subgroup sizes.

(SPC) Statistical Process Control Certification Practice Test

(SPC) Statistical Process Control Certification Practice Test

SPC Fundamentals 2