Control Chart Options (1989 Guidance)

 

See Also:

Shewhart-CUSUM Control Chart

This dialog is used to specify options for the Shewhart-CUSUM Control Chart.

 

 

 

Baseline Samples

This is the number of baseline or reference samples used to construct the control chart. The 1989 guidance recommends that at least 8 baseline samples known to be uncontaminated be available to construct the baseline mean and standard deviation. This value is used in intra-well comparisons only.

If the value entered here is positive, the value entered is the number of baseline samples. For a data set with 15 samples from the specified well, if a value of 8 is entered, the first 8 samples will be used to construct the baseline mean and standard deviation. The remaining seven samples will be plotted on the control chart and compared to background.

If the value enter here is negative, the magnitude of this value is the number of the most recent samples plotted on the control chart. For a data set with 15 samples from the specified well, if a value of -7 is entered, the first 15-7=8 samples will be used to construct the baseline mean and standard deviation. The remaining seven samples will be plotted on the control chart and compared to background.

Shewhart Control Limit (SCL)

The upper Shewhart control limit. The 1989 guidance recommends a value of 4.5 for this parameter.

 

Internal Decision Value (h)

The 1989 guidance recommends a value of 5 for this parameter.

 

Reference Value (k)

This indicates the displacement D that should be quickly detected such that k = D/2. The 1989 guidance recommends a value of 1 for this value, which will allow a displacement of 2 standard deviations to be detected quickly.

 

 

Fast Initial Response Multiplier

 

This is the multiplier to provide fast initial response (FIR). A value of zero provides no fast initial response. For fast initial response, a value of 0.5 is recommended. Fast initial response will increase the ability of the Shewhart-CUSUM control chart to rapidly detect shifts from the goal value.

 

Circle Exceedances

 

If this box is checked, data points exceeding the control limit will be drawn with a circle. This helps to distinguish points showing exceedance for those unfamiliar with control chart interpretation.

 

 

Plot Numeric Values

 

You can plot values next to points on the graph. Select values to plot here. Value options include standardized mean, cumulative sum, or average sample concentration.

 

 

Standardized Mean Connection Line

The style of the line that connects points of the standardized mean.

 

CUSUM Connection Line

 

The style of the line that connects points of the cumulative sum.

 

 

Background Mean Line

 

Select the style of the line for the background mean.