CChart is a c-chart for monitoring the count of the number of defects when defects are rare. Control limits are computed using the Poisson distribution. If defects are not rare NpChart should be used instead.

Namespace: Imsl.Chart2D.QC
Assembly: ImslCS (in ImslCS.dll) Version: 6.5.0.0

Syntax

C#
[SerializableAttribute]
public class CChart : ShewhartControlChart
Visual Basic (Declaration)
<SerializableAttribute> _
Public Class CChart _
	Inherits ShewhartControlChart
Visual C++
[SerializableAttribute]
public ref class CChart : public ShewhartControlChart

Remarks

The control limits are at

\bar{c}+k\sqrt{\bar{c}}
where \bar{c} is the mean number of defects per sample and k is the value of the "ControlLimit" attribute for the line.

By default, the chart contains an upper control limit line with k=3, a lower control limit line with k=-3, and a central line equal to \bar{c}. Additional control limits can be added. The method AddWeco adds control limits with k = -2, -1, 1, 2.

The lower control limit is computed using the Poisson distribution. First the probability of the number of defects being less than k (the "ControlLimit" value) standard deviations from the mean in a normal distribution is computed. The number of defects required to produce the same probability assuming a Poisson distribution, with the same mean, is then computed. The lower limit is set to be one more than this number of defects.

Inheritance Hierarchy

See Also