A measure of effectiveness and its measurement method

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Unformatted text preview: e costs have been expended at 50 percent of the cumulative time; in curve (3) with A = B = 0, it's 19 percent. Typically, JSC uses a 50 percent profile with A = 0 and B = 1, or a 60 percent profile with A = 0.32 and B = 0.68, based on data from previous projects. NASA Systems Engineering Handbook Systems Analysis and Modeling acquisition effort, but doesn't take into account the multiyear nature of that effort. The system engineer can use a set of "annual cost spreaders" based on the typical ramping-up and subsequent ramping-down of acquisition costs for that type of project. (See sidebar on beta curves.) Although some general parametric cost models for space systems are already available, their proper use usually requires a considerable investment in reaming time. For projects outside of the domains of these existing cost models, new cost models may be needed to support trade studies. Efforts to develop these need to begin early in the project life cycle to ensure their timely application during the systems engineering process. Whether existing models or newly created ones are used, the SEMP and its associated life-cycle cost management plan should identify which (and how) models are to be used during each phase of the project life cycle. 5.3 Effectiveness Definition and Modeling The concept of system effectiveness is more elusive than that of cost. Yet, it is also one of the most important factors to consider in trade studies. In selecting among alternatives, the system engineer must take into account system effectiveness, even when it is difficult to define and measure reliably. A measure of system effectiveness describes the accomplishment of the system's goals and objectives quantitatively. Each system (or family of systems with identical goals and objectives) has its own measure of system effectiveness. There is no universal measure of effectiveness for NASA systems, and no natural units with which to express effectiveness. Further, effectiveness is dependent on the context (i.e., project or supersystem) in which the system is being operated, and any measure of it must take this into account. The system engineer can, however, exploit a tew basic, common features of system effectiveness in developing strategies for measuring it. 5.3.1 Strategies for Measuring System Effectiveness Sy...
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