ARMY AL&T
FIGURE 1
decision, the PM must recognize this when deciding what to do.
Te colored regions help us understand the risk we’re taking when making a decision. Te green area contains 67 percent of the area in the distribution, and this tells us there is a 67 percent chance that the new software is better than the current soft- ware. We can also see that there is a 15 percent chance the two versions are equiv- alent (new software better but by less than 5 percent per the PM), and an 18 percent chance that the new software is actually worse in spite of the fact that it performed better in testing.
By understanding the information described above, the PM can make a risk- aware fielding decision by weighing the potential for fielding a better software against the risk of spending resources to field equivalent or inferior software. At a high level, there are three options:
PROBABLE CAUSE
Statistical analysis of the test data yields this result, which demonstrates the probability of detection. Understanding the meaning of the data is critical to making a risk-aware decision. (Image by the author)
Notice that the peak of the distribution is very close to 10 percent and is desig- nated by the black dot at the bottom of the distribution. Tis represents our best estimate of the improvement when using the new software, and should not be a surprise since the new software had a 10 percent greater success rate during testing.
However, because we have data, there is uncertainty about
limited the
true improvement that the new soft- ware would provide in the many events that would occur over the lifetime of a fielded system.
Tis uncertainty is represented by the black line at the bottom of the distribu- tion, which indicates the range of values 95 percent likely to contain the actual (and unknown) improvement. Te line ranges from -0.07 to 0.28, and this tells us that it is reasonable to conclude the new software results in an improvement of -7 percent (the new software is 7 percent less likely to detect a missile, and is inferior) to 28 percent (the new software is 28 percent more likely to detect a missile, and is better). Although the PM would prefer a definitive answer to the question “Is the new software better?”, it isn’t possible with the data available. To make a risk-aware
• Field the new software with a 67 percent chance that it improves probability of detection by at least 5 percent and some potential for at least 28 percent improve- ment. The risk is that the PM will spend possibly substantial resources to field the software while accepting a 33 percent chance that Soldiers are receiv- ing software that either degrades or does not sufficiently improve performance.
• Continue with the currently fielded software, save the cost of fielding and accept a 67 percent risk that Soldiers are not receiving improved software.
• Spend time and other resources to collect more data to more accurately understand the actual improvement provided by the new software.
Te actual decision the PM would make could also depend on other factors and isn’t important for now. Te point is that by
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