A statistical-analysis approach for system requirements definition and flowdown

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Title: A statistical-analysis approach for system requirements definition and flowdown
Author: Chollar, George W
Abstract: Statistical analysis methods are integrated with systems engineering to provide improvements in requirement definition and flowdown . A Method of Moments approach that supports the calculation of a response probability of noncompliance (PNC ) based on system properties and variables is developed . To achieve this result , the statistical properties for each system parameter are combined with system characteristics to predict the response and its statistical properties . This statistical analysis approach supports the allocation of variance for each system parameter when required or desired levels of response PNC are provided . The necessary relationships for calculating system response uncertainty and allocating variability are developed . A deterministic equation for a system requirement is used as the base model for the statistical analysis approach . A pseudo -model in the form of a second -order Taylor series expansion is created . Basic rules of statistics are applied to develop relationships for parameter variance allocation and the first four statistical moments of the system response . The resulting moment equations require the definition of counterpart statistics for the system variables (or parameters ) along with the definition of appropriate probability density functions . The family of empirical Johnson distributions is used to support the analysis objectives for the system parameters and response . Allocation of parameter variance and optimization of other statistical properties follow from calculations for the system response variance and PNC . In the development and application of the Method of Moments approach , system models with independent , correlated , and non -normally distributed random variables are considered . Comparison with established Monte Carlo methods indicate that the developed statistical -analysis approach provides comparable results . The methods developed in this research provide an anal5d :ical alternative to conventional empirical statistical -analysis methods used for predicting the statistical properties of a system response .
URI: http : / /hdl .handle .net /2346 /8659
Date: 2000-05


Chollar, George W A statistical-analysis approach for system requirements definition and flowdown. Doctoral dissertation, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /8659 .

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