MAKING NUMBERS COUNT


experiments to get more information and better prediction models for performance optimization,


sometimes using


FIGURE 1 signifi-


cantly less resources, with benefits for cost, schedule, and performance. Here are true examples of the power of statistics:


 In one experiment, the contractor proposed building and testing nearly 870 units,


at government


RESPONSE SURFACE


expense.


ARDEC’s statisticians used response surface optimization, a powerful fam- ily of “designed experiment” that allows modeling of interactions and curvature in the response, or “mea- sure of performance.” (See Figure 1.) Tus the team planned an experiment that required only 21 test units and yielded much better predictions. (See Figure 2.)


A small-caliber ammunition experi- ment proposed by a contractor called for more


than 12,000 samples.


ARDEC statisticians, using binary logistic regression, executed a success- ful test with 380 samples, resulting in meaningful


prediction models.


Te statisticians proposed an efficient sequential test strategy and more pow- erful statistical methods to reduce an IPT’s previously proposed usage of test assets from 450 to 30 units.  An experiment caliber


ammunition cutting-edge


to optimize a small- projectile was


designed using 18 runs by leverag- ing


screening


techniques, versus the IPT’s original proposal of nearly 650 runs.


 Simulation and probabilistic methods are being applied whenever appropri- ate, enabling IPTs in some instances to gain insight based on limited his- torical data, or even to eliminate certain test efforts altogether.


STATISTICAL DISCIPLINE Tese examples illustrate the utility of statistics in the hands of experienced,


114 Army AL&T Magazine January–March 2013 design


In one example of the true power of statistics, a contractor proposed building and testing nearly 870 units, at government expense. The professional statisticians in the Statistical Methods and Analysis (SM&A) Group of the U.S. Army Armament Research, Development, and Engineering Center (ARDEC) used response surface optimization, which allows modeling of interactions and curvature in the response, or “measure of performance,” to plan an experiment. (SOURCE: ARDEC SM&A Group)


competent, ethical practitioners. As


mentioned before, we are concerned with the true performance of a system, and that means minimizing the risk of false conclusions based upon the data. It


also means that we must be cognizant of the proper application of statistical principles and concepts, as it is possible to use statistical methods improperly to give stakeholder results that support the


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