Statistical Quality Control

Question 1

What are 4 assurance methods for quality control?

Answer 1

• Establishing standards
• Ensuring conformance to the standards
• Correcting faults
• Preventative measures

Question 2

What are Common (Non-Assignable) Causes?

Answer 2

Chance, or common, causes, are small random changes in the process that cannot be avoided.

The distribution of the changes’ magnitude follows a Standard or Normal distribution.

When this type of variation is suspected production continues as usual.

Question 3

What are Assignable causes?

Answer 3

Assignable causes are large variations. When this type of variation is suspected, the production process is stopped and a reason for the variation is sought.

Question 4

What are the three ways of identifying assignable causes?

Answer 4

• Change in mean
• Change in range/spread
• Change in distribution shape

Question 5

What are the two types of data used in SQC?

Answer 5

Variable data and Attribute data (discrete data)

Question 6

What is the summary of the control chart process?

Answer 6

1) Take periodic samples from a process
2) Plot the sample points on a control chart
3) Determin if the process is within limits
4) Fix the manufacturing process before defects occur

Question 7

What is a Type I error?

Answer 7

Probability of believing a process is out of control when it isnt (ie pure randmoness is present).

Known as producers risk

Question 8

What is a Type II error?

Answer 8

A Type II error occurs when it is concluded that a process is in control when it is actually not.

Known as consumers risk