I__. - International Military Testing Association

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requirements, but their number and complexity often makes trade off decisions
difficult because there i.s no context for their Cost. The literature has not
helped either. A U.S. Air Force review of 114 human factors studies from
1958-72 Eound that the physical characteristics of the stimulus were most
often the signif icant factors in performance outcomes and there were few
interactions.
But these studies tended to ignore the contribution of practice
or individual differences. This general finding suggested the multivariate
(holistic) approach that was subsequently employed by the Navy in over a
decade of simulator research, ranging from carrier landing, to air-to-ground
combat , to Vertical Take-Off and Landing (VTOL) studies. The strong inference
suggested by the results of these later studies was that people accounted for
the most variance in performance, followed by training manipulations, and then
by equipment variations.
In this work, what was surprising was the modest amount of performance
variance that could be accounted for by equipment features. In partitioning
the performance variances over numerous experiments, equipment accounted For
15-20%) trials of practice accounted for lo-25%. and people accounted for
50-80%, with error usually in the 25-50% range. Again, interactions were few
and far between. This implied that these main effects could be traded off if
you started with them in the first place! Thus was born Isoperformance. That
is, because some pilots are simply better than others, because repeated hops
are costly, and because costly changes in equipment features may produce
minimal changes in performance, we should concentrate on trade-offs among
these known relations to bring about desired goals rather than only one or
another mechanism. After the relative contributions are determined, a price
tag can be placed on all dimensions and the cheapest solution sought.
Isoperformance is therefore designed to accomp.lish Personnel, Training and
Equipment trade-offs. In the Isoperformance complete program, the term
Personnel can represent such features as sensory capabilities, cognitive and
information processing abilities, anthropometry, or test scores, such as the
Armed Services Vocational Aptitude Battery (ASVAB) scores, (presently the
default condition). The term Training can represent such features as
practice, sequence and series effects, learning, training regima and
schedules, or number of sessions. The default condition is trial of practice.
Similarly, the term Equipment can represent new vs. old, smart vs. dumb.
hi-fidelity vs. low-fidelity, or any general A vs. B conEiguration, which is
the default condition. The data sources for estimates of the scale values for
these variables can come from various origins, including lay opinion, the
scientific literature, explicit experiments, or technical data bases.
Isoperformance Curves
Figure 1 presents an illustration of IsoperEormance using two categories
and one equipment feature (the current technoloqy).
The Personnel category is divided into high- and low- to medium- aptitude
groups, the Training time allotted is 9 weeks, and the proport ion of people
that is desired to complete the training successfully is set at 50%. One can
see that it takes the high-aptitude group only 4 weeks to achieve the SM:~
proficiency level that it takes the low- and mediurr-aptitude group to achieve
in 8 weeks.