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QF20_CDF_NORMAL_ESTIMATE - Estimation of fractions of a normal distribution
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Task
This function computes estimated values of fractions F(x) and 1-F(x) for a given value x of a normally distibuted population with distribution parameters unknown. Sample results are required in summarized form only.
Example
If LSL and USL are the specification limits of a normally distributed characteristic then F(LSL) is the fraction of units in the population that are too small and 1-F(USL) is the fraction of units that are too big. Both fractions can be estimated from sample results using two calls of the present function.
CALL FUNCTION 'QF20_CDF_NORMAL_ESTIMATE'
EXPORTING SAMPLE_MEAN = XMEAN
SAMPLE_SIZE = N
SAMPLE_STDDEV = S
SPLITTING_VALUE = LSL
IMPORTING PROB_BELOW = FRACTION_BELOW_SPEC.
CALL FUNCTION 'QF20_CDF_NORMAL_ESTIMATE'
EXPORTING SAMPLE_MEAN = XMEAN
SAMPLE_SIZE = N
SAMPLE_STDDEV = S
SPLITTING_VALUE = USL
IMPORTING PROB_ABOVE = FRACTION_ABOVE_SPEC.
The nonconforming fraction F(LSL) + (1-F(USL)) is the sum of the two estimated values.
FRACTION_NONCONFORMING = FRACTION_BELOW_SPEC. + FRACTION_ABOVE_SPEC.
Statistical properties
The estimator used is unbiased. Of all unbiased estimators, it has mimimal variance.
References
- E.L. Lehmann, Theory of Point Estimation, John Wiley & Sons, New York 1983
- G.J. Liebermann, G.J. Resnikoff, Sampling Plans for Inspection by Variables, J. Amer. Statist. Assoc. 50, 457-516 (1955)
Parameters
PROB_ABOVEPROB_BELOW
SAMPLE_MEAN
SAMPLE_SIZE
SAMPLE_STDDEV
SPLITTING_VALUE
Exceptions
NOT_POSITIVEFunction Group
QF20BAL_S_LOG - Application Log: Log header data Addresses (Business Address Services)
This documentation is copyright by SAP AG.
Length: 2890 Date: 20240523 Time: 135402 sap01-206 ( 36 ms )
