compute control limits for the X chart - Maple Help

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ProcessControl[XControlLimits] - compute control limits for the X chart

Calling Sequence

XControlLimits(X, n, options)

Parameters

X

-

data

n

-

(optional) sample size

options

-

(optional) equation(s) of the form option=value where option is one of confidencelevel, ignore, rbar, or xbar; specify options for computing the control limits

Description

• 

The XControlLimits command computes the upper and lower control limits for the X chart. Unless explicitly given, the mean and the average of the moving ranges of two observations of the underlying quality characteristic are computed based on the data.

• 

The first parameter X is a single data sample, given as a Vector or list. Each value represents an individual observation.

Computation

• 

All computations involving data are performed in floating-point; therefore, all data provided must have type realcons and all returned solutions are floating-point, even if the problem is specified with exact values.

• 

For more information about computation in the ProcessControl package, see the ProcessControl help page.

Options

  

The options argument can contain one or more of the following options.

• 

confidencelevel=realcons -- This option specifies the required confidence level. The default value is 0.9973, corresponding to a 3 sigma confidence level.

• 

ignore=truefalse -- This option controls how missing values are handled by the XControlLimits command. Missing values are represented by undefined or Float(undefined). So, if ignore=false and X contains missing data, the XControlLimits command returns undefined. If ignore=true, all missing items in X are ignored. The default value is true.

• 

rbar=deduce or realcons -- This option specifies the average of the moving ranges of two observations.

• 

xbar=deduce or realcons -- This option specifies the mean value of the underlying quality characteristic.

Examples

withProcessControl:

infolevel[ProcessControl]:=1:

A:=33.75,33.05,34.00,33.81,33.46,34.02,33.68,33.27,33.49,33.20,33.62,33.00,33.54,33.12,33.84:

XControlLimitsA

32.2448378926038,34.8018287740628

(1)

l:=XControlLimitsA,confidencelevel=0.95

l:=32.2448378926038,34.8018287740628

(2)

See Also

infolevel, ProcessControl, ProcessControl[XChart], Statistics

References

  

Montgomery, Douglas C. Introduction to Statistical Quality Control. 2nd ed. New York: John Wiley & Sons, 1991.


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