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QRKT_STD_DEVIATION_SHEWHART - Algorithms for Shewhart chart for s with internal dispersion and mean line

General Data in Customer Master   rdisp/max_wprun_time - Maximum work process run time  
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Functionality

In the QM Customizing application, enter the function module QKRT_STD_DEVIATION_SHEWHART for the track of a quality control chart, if you want to use the standard deviation as a control value for a quantitative characteristic in order to detect the dispersion changes for a characteristic (s-chart).

The multiplicative factor for the chi-square distribution required for the calculation of the control limits is estimated on the basis of the internal dispersion of the total sample.

s = sqrt((s1**2 + ... + sN**2) / N)

An unbiased estimator for Sigma is positioned in the chart as a center line. It is calculated on the basis of the following formula:

M = s * c4(n)

c4(n) = sqrt((n-1)/2) * gamma(n/2) / gamma((n+1)/2))

In the function module's set-up parameters, you can propose the probabilities with which the the control limits will be exceeded, despite the fact that the location and dispersion of the process has not changed (statistical error of first kind).

Example

If, in an undisturbed process, 95% of the mean values are to be within the warning limits, 4% between the warning and action limits and 1% outside of the action limits, select the following parameter values:

Parameter 1,,0.995000
Parameter 2,,0.975000
Parameter 3,,0.025000
Parameter 4,,0.005000

If you do not require the warning limits, reset parameters 2 and 3 to the initial value 0.

Notes

When the control limits are calculated, it is assumed that the variances of the individual samples conform to a Chi-square distribution. This is often the case when the distribution of original values is not normal.

The function module is not suited for characteristics with a sample size of n=1.

Further information

Quality control charts in the QM component are described in the Implementation Guide and in the documentation.

Parameters

ES_QRKDY
E_LIMITRC
E_QAST
E_TESTSRC
I_CALCULATE_LIMITS
I_FPAR1
I_FPAR2
I_FPAR3
I_FPAR4
I_QASH
I_QAST
I_QPSH
I_STRUCTURE_OF_RESULTS
T_RESULTSTAB
T_SPURTAB

Exceptions

COMPUTING_ERROR
INVALID_STRUCTURE
MASTER_DATA_ERROR
MISSING_DATA
PROGRAMMING_ERROR

Function Group

QRKT

TXBHW - Original Tax Base Amount in Local Currency   TXBHW - Original Tax Base Amount in Local Currency  
This documentation is copyright by SAP AG.

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