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

Define what kind of problem would apply a systems analysis, What kind of pr...

What kind of problem would you apply a systems analysis to? Why?

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

Summarize the key points of the performance improvement, Briefly summarize ...

Briefly summarize the main points of the Performance Improvement article. Discuss one item that you have learned from the reading and how you might benefit from the information. (I

Explain what is the efficiency process, An assembly line currently has five...

An assembly line currently has five workstations and the time required for each is shown below 1. 42sec 2. 49 sec. 3. 32 sec. 4. 47 sec. 5. 42 sec. What is the efficiency process?

How feedback either promoted, How feedback, Goals Competence, and motive ha...

How feedback, Goals Competence, and motive has have either promoted or stunted performance in your own experiences at work.

Explain what entry mode would you use, You are the Vice-President for Inter...

You are the Vice-President for International Development of a small U.S. pharmaceutical company (located in Emeryville, California) which specializes in the development of new medi

Explain marketing problems and opportunities, The broad goal of _____ is to...

The broad goal of _____ is to identify and define both marketing problems and opportunities and to generate and improve marketing actions. advertising sales promotion publ

Explain the method of job evaluation, Explain the method of job evaluation....

Explain the method of job evaluation. Method of job evaluation: Following are the methods wherein job evaluation is done:- a) Ranking method. b) Classification method.

Explain the ohio-based company is covered by the nlra, The Ohio-based compa...

The Ohio-based company is covered by the NLRA. The CEO has heard rumblings that the employees may not be satisfied and are looking for representation. The CEO asked you, "If a unio

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