Standardised scores, Quality assurance and Control charts

Question 1

Standardised score formula

Answer 1

Standardised score= score-mean/standard deviation
If score is greater than mean, the standardised score will be positive. Otherwise the standardised score will be negative

Question 2

What is Quality Assurance?

Answer 2

It involves checking samples to ensure that the product of a manufacturing process meets the required standards

Question 3

What is a Control chart?

Answer 3

A time series chart that is used for Quality Assurance

Question 4

Warning Limits

Answer 4

Warning limits are set at +or- 2 standard deviations. 95% of the sample means should lie between 2+or- standard deviations. If a sample mean is between the warning limits, the product is acceptable.

Question 5

Action Limits

Answer 5

Action limits are set at +or- 3 standard deviations. 99,8% of the sample means should lie between the 3+or- standard deviations. If a sample mean is between the warning and action limits, another sample is taken immediately to see if there is a problem. If a sample mean falls outside the action limits, the process is stopped and the machinery is reset.