CQI CQI Statistical Process Control 1

Question 1

What is the primary purpose of a control chart?

Accepted Answer

To distinguish between common cause and special cause variation

Answer

Control charts are used to monitor processes over time and distinguish between normal (common cause) variation and abnormal (special cause) variation.

Question 2

Which control chart is used to monitor the proportion of defective items in a sample?

Accepted Answer

p-chart

Answer

The p-chart monitors the proportion of nonconforming units in samples and is an attribute control chart for fraction defective.

Question 3

What do the Upper Control Limit (UCL) and Lower Control Limit (LCL) represent on a control chart?

Accepted Answer

The boundaries within which process variation is expected due to common causes (±3σ)

Answer

UCL and LCL are calculated at ±3 standard deviations from the process mean and define the expected range of common cause variation.

Question 4

Which of the following is a signal of special cause variation on a control chart?

Accepted Answer

Eight consecutive points on the same side of the centerline

Answer

Eight consecutive points on the same side of the centerline (a Nelson/Western Electric rule) indicate a process mean shift, signaling special cause variation.

Question 5

An X-bar and R chart monitors:

Accepted Answer

Variable (continuous) data — subgroup means and ranges

Answer

The X-bar and R chart monitors variable (continuous) data by tracking subgroup averages (X-bar) and ranges (R) to detect process shifts and spread changes.

CQI - Certified Quality Inspector Practice Test

CQI - Certified Quality Inspector Practice Test

CQI CQI Statistical Process Control 1