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Non-Normal Process Capability EvaluatorNon-Normal Process Capability Evaluator
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Process capability evaluation done the traditional way, is based on an assumption that the data is Normally distributed. However, there are processes, which are inherently non-normal, and using assumptions of normality can lead to erroneous evaluation. This may lead to wrong decisions. In cases where the data is not normally distributed, the evaluation of Process Capability requires special techniques. Recognizing this, the recently updated SPC manual of AIAG (2nd Edition, July 2005) recommends the use of Non-normal process capability evaluation techniques to deal with such data.

Symphony’s Non-Normal Process Capability Evaluator, enables you evaluate non-normal process capability using one of the following methods :
  • Box-Cox power Transformation
  • Johnson Transformation system
  • Clements Method using Pearson Curves
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View Sceen Shot Box-Cox Transformation:
The Box-Cox transformation is used for transforming non-normal data. The Box-Cox Transformation uses the parameter Lambda. Non-Normal Process Capability Evaluator automatically selects the value of lambda so that the best possible transformation is done and data transforms as closely as possible to normality. Process Capability evaluation is done on the transformed data.

Johnson Transformation:
Johnson Transformation transforms your data to normality distribution using the Johnson distribution system. Johnson transformation internally evaluates several transform functions and optimally selects one from three families of distributions, which transform the data into a normal distribution. These distributions are bounded, lognormal, and unbounded (SB, SL & SU). Non-Normal Process Capability Evaluator selects the transform function such that the transformed data comes closest to Normality. Process Capability evaluation is done on the transformed data.

Clement's Method using Pearson Curves:
Clements’ method estimates capability indices based on evaluation of the skewness and kurtosis of the data. The method estimates percentiles and medians of the process distribution to define percentile based performance indices. Clements (1989) proposed method of determining percentiles based on Pearson family of distribution, which is used to determine capability indices.
Symphony’s Non-Normal Process Capability Evaluator is easy to use and gives a intuitive user experience. It enables you perform Process Capability analysis on Non-Normal processes without undue Math Anxiety.

The methods used by the Non-Normal Process Capability Evaluator are in line with the recommendations of the 2nd Edition (July 2005) of AIAG SPC Manual. 		Special Introductory Price :    US$ 29   per license, installed on one computer.
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