This proposal requests three additional models to be added to the LVF delay, transition, and constraint variation modeling set.  These models will represent the three top central moments of the distributions. They will adopt syntax similar as the existing LVF sigma constructs. 
 

The new constructs proposed do not replace the existing ocv_sigma_* constructs already approved for LVF.  It is the responsibility of the LVF consumer applications to decide how best to utilize these new constructs as their needs and capabilities dictate. 
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Mean-shift Extension 
 

New ocv_mean_shift_* tables are proposed for augmenting the variation modeling for delays, transitions, and constraints.   The new table data will represent the difference between the nominal value expressed in Liberty and the mean value of the distribution:   
 

d_mean -  d_nominal

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Standard Deviation Extension 
 

Also being proposed, are new ocv_std_dev_* tables which represent the standard deviation of the distribution using the common definition:

 

E[(d-d_mean)2  ]^1/2 

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Skewness Extension 
 

The final constructs being proposed as part of this set of extensions are the ocv_skewness_* tables.  Skewness is the third-order moment of a distribution and provides a measure of the symmetry of the distribution.  It is defined in units of time as: 
 

E[(d-dmean)3  ]^1/3

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