Appropriate Statistical Models Statistical models that are based on empirically supported assumptions should be used in test design for and evaluation of system reliability (as well as for system effectiveness). It is typical for the service test agencies to make use of a specific model (the exponential model) of the time to first failure, in reliability design and evaluation. Use of this model, when inappropriate, can often result in unnecessarily large test sizes and inappropriate results for significance tests. There are many other models that are often more appropriate for this kind of application.

Software-Intensive Systems Operational tests of software-intensive systems should employ a usage-based perspective, in order to demonstrate that the system is fit for its intended use. When testing schedules and budgets are tightly constrained, usage-based testing yields the highest practical reliability because if failures are identified, they are likely to be the high-frequency failures.

In summary, by making testing a more useful and integrated component of military system development, by adopting up-to-date statistical practices, and by changing the paradigm in which test and evaluation is used in defense system development, the acquisition of military systems will become even more effective and efficient, and benefit from considerable savings in system life-cycle costs.



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