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Topic: Control chart

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Statistical process control

Western Electric rules

Standard deviation

Random sampling

Variance

Normal distribution

Calibration (statistics)

Range (statistics)

Binomial distribution

Median

Probability

Mathematical model

Statistics

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Total Quality Management

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	Control Charts as a tool in SQC
		Shewhart developed the control charts as an statistical approach to the study of manufacturing process variation for the purpose of improving the economic effectiveness of the process.
		A typical control chart is a graphical display of a quality characteristic that has been measured or computed from a sample versus the sample number or time.
		Control chart is a device for describing in a precise manner what is meant by statistical control.
	deming.eng.clemson.edu /pub/tutorials/qctools/ccmain1.htm (773 words)

	New Page 1
		Control of the process average or mean quality level is usually with the control chart for means, or the x bar chart.
		The control of the process range is done by using the control chart for range, or the R chart.
		Control charts are a highly specialized tool that indicate a process performance according to the characteristics of the process.
	web.njit.edu /~wfg9444/ControlCharts.htm (2332 words)

	Control Chart Interpretation
		Control charts are running records of the performance of the process and, as such, they contain a vast store of information on potential improvements.
		While some guidelines are presented here, control chart interpretation is an art that can only be developed by looking at many control charts and probing the patterns to identify the underlying system of causes at work.
		Control charts serve as historical records of the learning process and they can be used by others to improve other processes.
	www.qualityamerica.com /knowledgecente/articles/CQEIVH3d.html (1122 words)

	Control Charts
		Acceptance control charts for high Cpk processes, where the control limits are placed at a fixed distance from the specification limits rather than the centerline of the chart.
		Control limits are added to the plot to signal unusually large deviations from the centerline, and run rules are employed to detect other unusual patterns.
		For a control chart to be effective, it must be able to distinguish between situations in which the process is operating as expected and those in which it has deviated seriously from its target values.
	www.statgraphics.com /control_charts.htm (960 words)

	Quality Control Charts
		In both line charts, the horizontal axis represents the different samples; the vertical axis for the X-bar chart represents the means for the characteristic of interest; the vertical axis for the R chart represents the ranges.
		The types of charts are often classified according to the type of quality characteristic that they are supposed to monitor: there are quality control charts for variables and control charts for attributes.
		For attribute control charts (C, U, Np, or P charts), the estimate of the variability of the process (proportion, rate, etc.) is a function of the process average (average proportion, rate, etc.; for example, the standard deviation of a proportion p is equal to the square root of p*(1- p)/n).
	www.statsoft.com /textbook/stquacon.html (4479 words)

	Cusum Control Chart
		Similar to the exponentially weighted moving average control chart, it is better than the standard xbar control chart for detecting small shifts in the process mean.
		FIR cusum control charts are recommended for the case where there may be multiple causes for an out-of-control signal and you want to detect as quickly as possible if the process is still out of control after the process is restarted.
		CUSUM CHART is a synonym for CUSUM CONTROL CHART.
	www.itl.nist.gov /div898/software/dataplot/refman1/auxillar/cusum.htm (519 words)

	SixSigma First - Article \| SPC Control Charts
		Control charts were developed as a monitoring tool for SPC by Dr. Shewhart; they are among the most important tools in the analysis of production process variations.
		A typical control chart is made up of at least four lines: a vertical line that measures the levels of the samples' means, the two outmost horizontal lines represent the UCL and the LCL and the Center Line represents the mean.
		What is meant by in control process is not a total absence of variation but instead, when the variations are present, they exhibit a random pattern, they are not outside the control limits and based on past experience, they can be predicted and are strictly due to common causes.
	www.sixsigmafirst.com /controlcharts1.htm (2450 words)

	» The Road to Six Sigma - Control Charts
		For simplicity’s sake, we will focus on control charts for variable individual readings because this chart is usually most useful in understanding and improving business processes.A control chart for individuals is used when a sample size of one is the only sample available.
		The purpose of such a chart is to measure the variations within the sample of ten specimens and compare those variations to the variations between samples.
		Control charts are a good way to determine if a test change to a process, say a promotional offer, has a statistically significant effect on the process.
	www.bizmanualz.com /information/2006/10/31/the-road-to-six-sigma-control-charts.html (1070 words)

	Control chart: Is your process consistent? Predictable? A Shewhart control chart (SPC chart) can tell you. (Site not responding. Last check: 2007-10-31)
		There are many different subspecies of control charts which can be applied to the different types of process data which are typically available.
		Control limits on a control chart are commonly drawn at 3s from the center line because 3-sigma limits are a good balance point between two types of errors:
		The reason that 3-sigma control limits balance the risk of error is that, for normally distributed data, data points will fall inside 3-sigma limits 99.7% of the time when a process is in control.
	www.skymark.com /resources/tools/control_charts.asp (667 words)

	Elizabeth Clarkson - A Process Control Primer
		The x bar chart measures the average of the process; the R chart measures its dispersion, or variability.
		Control charts allow you to distinguish between normal, expected variation, called common cause variations, and unusual variations, known as special cause variations, which require action.
		The upper and lower control limits (UCL and LCL) are computed based on R bar and a pair of constants D3 and D4, which depend on the sample size and must be looked up in a table of control chart constants.
	members.cox.net /bethclarkson/Articles/ControlCharts.html (621 words)

	Control Charts (Site not responding. Last check: 2007-10-31)
		Control charts can be used to gain a better understanding of how a particular process is performing.
		Control charts use subgroups of data and display the average of those subgroups as individual points as well as a range chart that plots the difference of the highs and lows of the points included in a subgroup.
		Control limits for XR charts are computed from the Grand Average (the average of the subgroup averages) and the range.
	www.stonemont.com /stonemont/webhelp/DataAnalysis/control_charts.htm (862 words)

	The Control Chart
		Control charts are generally used in a production or manufacturing environment and are used to control, monitor and IMPROVE a process.
		The use of control charts is called "process control." In reality, however, a trend will develop that indicates the process is leading away from the center line, and corrective action is usually taken prior to a point exceeding one of the control limits.
		This chart is particularly useful in that it shows changes in mean value and dispersion of the process at the same time, making it a very effective method for checking abnormalities within the process; and if charted while in progress, also points out a problem in the production flow in real time mode.
	www.qualityspctools.com /control.html (2344 words)

	Which control chart should you use?
		Correct control chart selection is a critical part of creating a control chart.
		If the wrong control chart is selected, the control limits will not be correct for the data.
		The type of control chart required is determined by the type of data to be plotted and the format in which it is collected.
	www.qualityadvisor.com /library/controlchartselection.php (378 words)

	WPF Chart Control With Pan, Zoom and More - The Code Project - Vista / .NET 3.0
		My chart control is useful in that it includes Pan/Zoom, has a clipboard helper that copies the chart to the clipboard in a resolution that the user desires, adds data to the image in the clipbaord so that the user can paste a bitmap image or past tab separated chart line values into a spreadsheet.
		While this chart control is quite basic right now I intend to add other features as they are required such as databinding to static and dynamic data sources with dynamic giving the chart an animated appearance, pipe shaded bars for bar charts, and other fancy chart primitives.
		In actual fact the current implementation of the chart control picks gridlines for the X axis that are multiples of powers of 12 as it has only been used for showing months on the X axis.
	www.codeproject.com /useritems/swordfishcharts.asp (2167 words)

	Control Chart (part 2: Types of Control Chart)
		A Control Chart should have at least 25 points on it, which can mean several hundred measurements are needed.
		Variables charts are more sensitive to change than Attributes charts, but can be more difficult both in the identification of what to measure and also in the actual measurement.
		The right attribute chart is also selected based on the whether there is constant number of measurements in each point (subgroup) on the chart.
	syque.com /quality_tools/tools/Tools69.htm (524 words)

	Curious Cat Management Encyclopedia, Dictionary, Glossary - Definitions of Management Terms: Control Chart, Upper ...
		Control Chart - graph of data used to determine when a result should be explored as a special cause.
		Using control charts the only time special cause analysis is used is when the result was above the upper control limit or below the lower control limit.
		Control Charts as a Tool in Data Quality Improvement by Carl E. Pierchala, Ph.D. and Jyoti Surti, B.S with the National Highway Traffic Safety Administration, 1999.
	curiouscat.com /management/controlchart.cfm (401 words)

	Control Chart Also Called: Statistical Process Control
		Control charts for variable data are used in pairs.
		The top chart monitors the average, or the centering of the distribution of data from the process.
		Control charts for attribute data are used singly.
	www.asq.org /learn-about-quality/data-collection-analysis-tools/overview/control-chart.html (666 words)

	Statistical Process Control (Site not responding. Last check: 2007-10-31)
		A primary tool used for SPC is the control chart, a graphical representation of certain descriptive statistics for specific quantitative measurements of the manufacturing process.
		Several different descriptive statistics can be used in control charts and there are several different types of control charts that can test for different causes, such as how quickly major vs. minor shifts in process means are detected.
		Control charts are also used with product measurements to analyze process capability and for continuous process improvement efforts.
	reliability.sandia.gov /Manuf_Statistics/Statistical_Process_Control/statistical_process_control.html (373 words)

	XmR Control Chart
		A control chart is a run chart which includes statistically determined limits, calculated from the data of the process.
		Control limits allow you to analyze the data to determine if variation is due to common causes or to a special cause.
		Given that the upper control limit is 18.74, any point larger than 18 would be an outlier and, therefore, signal a possible special cause of variation.
	mot.vuse.vanderbilt.edu /mt322/Control.htm (461 words)

	Control Chart - Saferpak.com
		In 1924, whilst working at Bell Labs Dr Walter A.Shewhart (the father of Statistical Quality Control - SQC) first conceived the terms "assignable-cause" and "chance-cause" variation and developed the control chart as a statistical approach for distinguishing between them.
		Shewhart stressed that bringing a production process into a state of "statistical control", where there is only chance-cause variation, and keeping it in control, is necessary to predict future output and to manage a process economically.
		The guide includes an overview of control charts, when to use them, how to use them, how to interpret results; as well as exercises for getting started...
	www.saferpak.com /control_chart.htm (310 words)

	cause and effect, control chart. customers, cability
		Control chart A chart that indicates upper and lower statistical control limits, and an average line, for samples or subgroups of a given process.
		If all points on the control chart are within the limits, variation may be ascribed to common causes and the process is deemed to be "in control." If points fall outside the limits, it is an indication that special causes of variation are occurring, and the process is said to be "out of control."
		If variation exceeds the control limits, then the process is being affected by special causes and is said to be "out of control." A control limit is not the same as a specification limit.
	www.adamssixsigma.com /Glossary_of_terms/six_sigma_glossary_C.htm (3024 words)

	How to Create a Control Chart - WikiHow
		Control charts are an efficient way of analyzing performance data to evaluate a process.
		Control charts have many uses; they can be used in manufacturing to test if machinery are producing products within specifications.
		By creating a control chart you could see how students were performing in relations to the mean.
	www.wikihow.com /Create-a-Control-Chart (658 words)

	SPCView Statistical Process Control Analysis Software - Process Control Chart Screen
		Each control point is either a deviation from the nominal value shown on the Process Control Data Screen, a deviation from the declared value of a check standard, a deviation from the mean of sampled process data, or a deviation between the current measured value and the measured value of the previous control point.
		The control chart also shows the upper control limit (UCL) and lower control limit (LCL) defined on the Process Control Data screen and a linear fit to the plotted data.
		Hardcopy reports of SPC analysis results and of the control chart can be generated through the use of the SPC Report Options Screen accessed by clicking Report on the Menu bar and selecting the Print option.
	www.isgmax.com /spc_screens/spc_control_chart.htm (583 words)

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