Sample mean chart - control charts for variables, Operation Management

Assignment Help:

Sample Mean Chart - Control Charts for Variables

This figure depicts a typical means chart, on which sample means would be progressively plotted, left to right. Two sets of control limits have been drawn symmetrically about the process population mean (estimated as the grand mean of several samples). The inner pair, the upper and lower warning limits, are positioned ±1.96 standard errors (s) above and below the population mean. For a stable process, there is a 1 in 40 chance that a sample mean will exceed the upper warning limit, and likewise for the lower warning limit. The outer pair, the upper and lower action limits, are positioned ±3.09s above and below the population mean. Again, for a stable process, there is only a 1 in 1000 chance of a sample mean breaching the upper limit, and likewise for the lower limit. If we determine the ranges of several samples, we can compute the average sample range (¯R). Remembering that the standard error s = σ / √n, we can take advantage of the findings of a statistician, Hartley, who quantified the relationship: σ = ¯R/dn where dn is a coefficient which varies with sample size. Hartley's constants (dn), for sample sizes 2 to 6, are presented in this table.

2077_Sample Mean Chart - Control Charts for Variables.png

For convenience, the coefficients 1.96/dn √n and 3.09/dn √n have been calculated for a series of sample sizes. These values are presented as A' 0.025 and A' 0.001 in this table.

Sample size             A'0.025                A'0.001 

2                                  1.23                 1.94 

3                                  0.67                 1.05 

4                                  0.48                 0.75 

5                                  0.38                 0.59 

6                                   0.32                0.50

The final expressions are, therefore:

Warning limits = μ+A'0.025 ¯R

Action limits = μ+A'0.001 ¯R


Related Discussions:- Sample mean chart - control charts for variables

Economical management of a company, Consider a fast-food restaurant that is...

Consider a fast-food restaurant that is trying to improve its service during the 12:00 - 2:00 lunch period.  Right now the restaurant employs 5 different single-channel queues, but

Explain ennoblement in addition to the primary deliverable, Almost all proj...

Almost all project have deliverables dealing with documentation and customer ennoblement in addition to the primary deliverable

Describe what is the total cost of a package, The Fido Dog Food Company wis...

The Fido Dog Food Company wishes to introduce a new brand of dog biscuits (composed of chicken and liver-flavoured biscuits) that meets certain nutritional requirements. The liver-

Explain accommodations for employees with mental illness, What do you think...

What do you think constitutes reasonable accommodations for employees with mental illness? Please support your responses. cited and reference. Is there a place in the workforce for

Explain breached claimed contract, On September 1, Jennings, a used-car dea...

On September 1, Jennings, a used-car dealer, wrote a letter to Wheeler in which he stated, "I have a 1955 Thunderbird convertible in mint condition that I will sell you for $13,500

Explain distinction between e-business and e-commerce, Why does the Baltzan...

Why does the Baltzan text draw a distinction between e-business and e-commerce? • The Baltzan text lists four challenges for Web-based e-business (pp. 103 - 104). See i

Turnaround at the preston plant, what are the most significant events in th...

what are the most significant events in the story of how the plant survived because of the adoption of quality-based principles?

Explain organization culture importance to business success, Describe organ...

Describe organization culture. Provide a definition and explanation of its importance to business success?

What steps must to be taken to maximize the sales-price, Identify key gaps ...

Identify key gaps in planning for the exit. Provide recommendations on the exit strategy. Is the sale the right one? What steps ought to be taken to maximize the sales-price? What

Define sociotechnical systems theory, Discuss sociotechnical systems theory...

Discuss sociotechnical systems theory and contrast it with the open systems theories of organization development?

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd