Control charts for attributes - statistical process control, Operation Management

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

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
Related Questions
Revisit the Automobile Driver's License office example. a. What is the direct labour utilization for the process shown in figure 7.6a? b.What is the direct labour utilization for

A _____ is a group of products that are closely related because they satisfy a class of needs, are used together, are sold to the same customer group, are distributed through the s

What do you think will happen to HRM in the future? What do you think of this prediction for HRM? Is it likely to come true? If so, why? If not, why not? Cited/References

A call center employs 1,000 agents. Every month 50 employees leave the company and 50 new employees are hired. How long does the average agent work for this call center?

Difference between production Planning and Control Many people are of the view that production planning embraces both planning and control. In the broader sense, production pla

What are the different network perspectives in innovative research? Why do authors differ in how they define innovation networks? How can networks influence actions of its members?

Knight, Inc., has issued a three-year bond that pays a coupon of 5.00 percent. Coupon payments are made semi-annually. Given the market rate of interest of 3.70 percent, what is th

The Toys-R-4-U Company has developed two new toys for possible inclusion in its product line. Setting up the production facilities to begin production would cost $50,000 for toy 1

The Bawl Corporation supplies alloy ball bearings to auto manufacturers in Detroit. Because of its specialized manufacturing process, considerable work-in-process and raw materials