Control Charts for Attributes - Statistical Process Control

Attribute data assume only two values, such as pass/fail or good/bad: they are counted rather than measured. Many quality characteristics can only be monitored in this way, such as the soundness of a soldered connection or the absence of components on a printed circuit board. Before proceeding further, a distinction must be made between defectives and defects. The term defective refers to a non-conforming item of output. A defect is a non-conforming feature of a single item of output: such an item may have more than one defect. Control charts for attributes have several advantages:

• Collection of attribute data does not require measurement equipment and the skills to use them
• They can be used to monitor any process, since the process output can be judged as either conforming or non conforming
• Different attributes may be recorded on a single chart.

 

On the other hand, they have the following disadvantages:

• Sample sizes are generally larger than for variables charts. Ideally, the sample size should be chosen such that, on average, at least one defective/defect is found in the sample
• Attribute data do not indicate degrees of defectiveness: a non conforming item may be slightly defective or greatly defective.

 

Several attributes control charts have been devised, but those most commonly used are those described below. Two charts that look for defective items are discussed - the p-chart that looks at the proportion of defectives when the sample size is variable, and the np- chart that looks for the proportion of defectives in a constant sample size. Another sort of chart - the c-chart - is also described. This looks for the number of defects on an item.

Posted Date: 3/16/2013 1:32:39 AM | Location : United States

Ask an Expert

Related Discussions:- Control charts for attributes - statistical process control, Assignment Help, Ask Question on Control charts for attributes - statistical process control, Get Answer, Expert's Help, Control charts for attributes - statistical process control Discussions

Write discussion on Control charts for attributes - statistical process control
Your posts are moderated

Write your message here..

Related Questions

Explain project supply and materials budget, Case 11-3 Budget the topic for... Case 11-3 Budget the topic for this week's assignment is taken from our text (INF336 2010, Mcgraw-Hill) and refers to the City of Granston Case 11-3 at the end of Chapter 11. Using

Explain market-driven approach to meeting customer, Provide specific exampl... Provide specific examples of ways that Pitney Bowes has aligned diversity goals with a market-driven approach to meeting customer needs.

Explain what organizations currently utilize six sigma, What is Six Sigma? ... What is Six Sigma? Who started it? What organizations currently utilize Six Sigma

Explain research on leader-member exchange, Write a 750-1,000-word paper th... Write a 750-1,000-word paper that analyzes the two leadership case studies, "Coach Knight: A Will to Win" and "Coach K: A Matter of the Heart." Address the following questions a

Preparing the research design, Preparing the Research Design: Researc... Preparing the Research Design: Research design is the conceptual structure within which research should be conducted. A research design specifies the methods and procedure fo

Who all are stakeholders affected by the stores'' decisions, Neda operates ... Neda operates a small convenience store in a southern town that has a high tourist draw. After several years of operating the store, Neda has decided to no longer sell tobacco prod

Describe the concepts of empowerment, Explain the concepts of empowerment, ... Explain the concepts of empowerment, self-managed teams, and cross-functional teams, and develop an essay that argues for their inclusion in either a tall or flat organizational st

Imagine this is the only position of its kind organization, Imagine this is... Imagine this is the only position of its kind in the organization. From this perspective, design a performance appraisal program to assess your job performance.

A firm plans to start production of a new small appliance, A firm plans to ... A firm plans to begin production of a new small appliance. The manager must decide whether to purchase the motors for the appliance from a vendor at $7 each or to produce them in-h

Describe the differences between a 3rd party beneficiary, Explain the diffe... Explain the differences between a 3rd party beneficiary and a 3rd party assignee. Why are assignments of contracts so important for our free enterprise economy?