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# 3.25. RiskSixSigma Property Function

Applies to: @RISK 5.x–7.x

Where should I use the RiskSixSigma( ) property function? Should it be part of RiskOutput( ) or RiskCpk( )?

The standard way is to use RiskSixSigma( ) with RiskOutput( ). That tells @RISK to put six-sigma labels on the graphs, and extra statistics in the statistics grid. It also lets you use the six-sigma worksheet functions to calculate Cpk and many other statistic functions. (In @RISK, click Insert Function » Statistic Functions » Six Sigma.)

For example, suppose you have an output in cell A1 that looks like this:

`=RiskOutput(,,,RiskSixSigma(0,1,.5))+`formula

If you put the formula `=RiskCpk(A1)` in another cell, @RISK will do the Cpk calculation using those LSL/USL/Target values. By doing it this way, you associate the six-sigma properties with the calculated output, and all statistic functions will use the same values.

Does that mean that I should never put a RiskSixSigma( ) inside RiskCpk( )?

There are two situations where you would want to place a RiskSixSigma( ) property function inside a statistic function such as RiskCpk( ):

• You may have an output you don't want to apply six-sigma properties to, but you still want to compute the Cpk for it with a certain set of parameters.  For example, you have a regular output in cell A2 with no six-sigma properties. In another cell, you can place the formula `=RiskCpk(A2,,RiskSixSigma(0,1,.5))` to get the Cpk assuming those LSL, USL, and Target values.

• You may want to calculate the Cpk for an output with a different set of parameters — for instance, to make a table of different Cpk values for different LSL/USL pairs. Using the sample output formula mentioned above for cell A1, you might have `RiskCpk(A1,,RiskSixSigma(0,1,1.5))`. This would override the six-sigma parameters the output normally has in favor of the ones embedded in the Cpk function.

How are the arguments to RiskSixSigma( ) used in computing Six Sigma statistic functions?

In @RISK, please click Help » Example Spreadsheets » Six-Sigma » Six Sigma Functions.docx. The first section of that document explains where each pf the five arguments to RiskSixSigma( ) is used. Following that are technical details of each of the 19 statistic functions, including computational formulas.

Additional keywords: Cp, RiskCp, Cpk, RiskCpk, Cpm, RiskCpm, DPM, RiskDPM

Last edited: 2015-06-19