Sample Range Chart - Control Charts for Variables

Whilst the sample mean chart provides control over the process setting, it provides no protection from change (increase) in the standard deviation of the process output. The second control chart (shown here) provides this by means of control limits set out from the average sample range (¯R) , determined when the process was stable.

Again, the control limits are established as 1-in-40 warning and 1-in-1000 action limits. They are determined by multiplying the average sample range (¯R) by the appropriate D' coefficient from the table below.

Upper action limit = D'_0.9999 ¯R

Upper warning limit = D'_0.975 ¯R

Lower warning limit = D'_0.025 ¯R

Lower action limit = D'_0.001 ¯R

In practice, the lower control limits are often omitted, the reasoning being that exceptionally low range values represent welcome consistency. However, such low-probability results are unlikely to be produced by a stable process, and may, in fact, be an indication that the measurements are incorrect.

Posted Date: 3/15/2013 6:05:46 AM | Location : United States

Ask an Expert

Related Discussions:- Sample range chart - control charts for variables, Assignment Help, Ask Question on Sample range chart - control charts for variables, Get Answer, Expert's Help, Sample range chart - control charts for variables Discussions

Write discussion on Sample range chart - control charts for variables
Your posts are moderated

Write your message here..

Related Questions

Dipict a competency model, Develop a competency model of a job held by a fr... Develop a competency model of a job held by a friend, spouse or partner

MBA, MBA, Operation Management Q3. What do you understand by “line balancin... MBA, Operation Management Q3. What do you understand by “line balancing”? What happens if balance doesn’t exist?

General questions, wanna know how long it takes to receive a paper wanna know how long it takes to receive a paper

Define the key planning factors for competitive success, What are the key p... What are the key planning factors for competitive success? Provide an example of an organization that has achieved competitive success through planning. Provide an example of an or

Explain risks to a broad generic business strategy, What are some drawbacks... What are some drawbacks and risks to a broad generic business strategy? To a focused strategy?

Explain business as a sole proprietorship, Conway just received his contrac... Conway just received his contractor's license in the state of Virginia. For years, Conway did light construction work for a few commercial accounts. He was very successful and had

Plant location evaluation methods.., i need calculated examples using the m... i need calculated examples using the methods of plant location evaluation.how are they calculated?

Contents of an operations strategy , Contents of an Operations Strategy  ... Contents of an Operations Strategy  The contents of an operations strategy is the policies, plans, performance targets which the organisation wishes to achieve. To determine

Criteria for a good layout, Criteria for a Good Layout Maximum Fl... Criteria for a Good Layout Maximum Flexibility: A good layout will be one which can be rapidly modified to meet changing circumstances. In this context particular attent

Explain activity immediate predecessor normal time, The Scott Corey account... The Scott Corey accounting firm is installing a new computer system, and several things must be done to make sure the system works properly. The following table provides informatio