This preview shows page 1. Sign up to view the full content.
Unformatted text preview: outside, independent corroboration.
Responsiveness of a model is a measure of its
power to distinguish among the different alternatives
being considered in a trade study. A responsive lunar
base cost model, for example, should be able to
distinguish the costs associated with different system
architectures or designs, operations concepts, or
Another desirable model characteristic is
transparency, which occurs when the model's
mathematical relationships, algorithms, parameters,
supporting data, and inner workings are open to the
user. The benefit of this visibility is in the traceability of
the model's results. Not everyone may agree with the
results, but at least they know how they were derived.
Transparency also aids in the acceptance process. It is
easier for a model to be accepted when its
documentation is complete and open for comment.
Proprietary models often suffer from a lack of acceptance because of a lack of transparency.
Upfront user friendliness is related to the ease
with which the system engineer can learn to use the
model and prepare the inputs to it. Backend user
friendliness is related to the effort needed to interpret
the model's results and to prepare trade study reports
for the tentative selection using the selection rule.
5.1.3 Selecting the Selection Rule The analytical portion of the trade study process
serves to produce specific information on system
effectiveness, its underlying performance or technical
attributes, and cost (along with uncertainty ranges) for a
few alternative system architectures (and later, system
designs). These data need to be brought together so
that one alternative may be selected. This step is
accomplished by applying the selection rule to the data
so that the alternatives may be ranked in order of
The structure and complexity of real world decisions in systems engineering often make this ranking a
difficult task. For one, securing higher effectiveness
almost always means incurring higher costs and/or
facing greater uncertainties. In order to choose among
alternatives with different levels of effectiveness and
costs, the system engineer must understand how much of one is worth in terms of...
View Full Document