DATAWorks Sessions Archive

Jones and Nachtsheim (2011) introduced a class of three-level screening designs called definitive screening designs (DSDs). The structure of these designs results in the statistical independence of main effects and two-factor interactions; the absence of complete confounding among two-factor interactions; and the ability to estimate all quadratic effects. Because quadratic effects can be estimated, DSDs can allow for the screening and optimization of a system to be performed in one step, but only when the number of terms found to be active during the screening phase of analysis is less than about half the number or runs required by the DSD (Errore, et al., 2016). Otherwise, estimation of second-order models requires augmentation of the DSD. In this paper we explore the construction of series of augmented designs, moving from the starting DSD to designs capable of estimating the full second-order model. We use power calculations, model-robustness criteria, and model-discrimination criteria to determine the number of runs by which to augment in order to identify the active second-order effects with high probability.

The process for testing military systems which are largely software intensive involves techniques and procedures often different from those for hardware-based systems. Much of the testing can be performed in laboratories at many of the acquisition stages, up to operational testing. Testing software systems is not different from testing hardware-based systems in that testing earlier and more intensively benefits the acquisition program in the long run. Automated testing of software systems enables more frequent and more extensive testing, allowing for earlier discovery of errors and faults in the code. Automated testing is beneficial for unit, integrated, functional and performance testing, but there are costs associated with automation tool license fees, specialized manpower, and the time to prepare and maintain the automation scripts. This presentation discusses some of the features unique to automated software testing and offers a framework organizations can implement to make the business case for, to organize for, and to execute and benefit from automating the right aspects of their testing needs. Automation has many benefits in saving time and money, but is most valuable in freeing test resources to perform higher value tasks.

The process for testing military systems which are largely software intensive involves techniques and procedures often different from those for hardware-based systems. Much of the testing can be performed in laboratories at many of the acquisition stages, up to operational testing. Testing software systems is not different from testing hardware-based systems in that testing earlier and more intensively benefits the acquisition program in the long run. Automated testing of software systems enables more frequent and more extensive testing, allowing for earlier discovery of errors and faults in the code. Automated testing is beneficial for unit, integrated, functional and performance testing, but there are costs associated with automation tool license fees, specialized manpower, and the time to prepare and maintain the automation scripts. This presentation discusses some of the features unique to automated software testing and offers a framework organizations can implement to make the business case for, to organize for, and to execute and benefit from automating the right aspects of their testing needs. Automation has many benefits in saving time and money, but is most valuable in freeing test resources to perform higher value tasks.

The growing complexity of interactive systems requires increasing amounts of effort to ensure reliability and usability. Testing is an effective approach for finding and correcting problems with implemented systems. However, testing is often regarded as the most intellectual-demanding, time-consuming, and expensive part of system development. Furthermore, it can be difficult (if not impossible) for testers to anticipate all of the conditions that need to be evaluated. This is especially true of human-machine systems. This is because the human operator (who is attempting to achieve his or her task goals) is an additional concurrent component of the system and one whose behavior is not strictly governed by the implementation of designed system elements. To address these issues, researchers have developed approaches for automatically generating test cases. Among these are formal methods: rigorous, mathematical languages, tools, and techniques for modeling, specifying, and verifying (proving properties about) systems. These support model-based approaches (almost exclusively used in computer engineering) for creating tests that are efficient and provide guarantees about their completeness (at least with respect to the model). In particular, model checking can be used for automated test case generation. In this, efficient and exhaustive algorithms search a system model to find traces (test cases) through that model that satisfy specified coverage criteria: descriptions of the conditions the tests should encounter during execution. This talk focuses on a formal automated test generation method developed in my lab for creating cases for human-system interaction. This approach makes use of task models. Task models are a standard human factors method for describing how humans normatively achieve goals when interacting with a system. When these models are given formal semantics, they can be paired with models of system behavior to account for human-system interaction. Formal, automated test case generation can then be performed for coverage criteria asserted over the system (for example, to cover the entire human interface) or human task (to ensure all human activities or actions are performed). Generated tasks, when manually executed with the system, can serve two purposes. First, testers can observe whether the human behavior in test always produces the system behavior from the test. This can help analysts validate the models and, if no problems are found, be sure that any desirable properties exhibited by the model hold in the actual system. Second, testers will be able to use their insights about system usability and performance to subjectively evaluate the system under all of conditions contained in the tests. Given the coverage guarantees provided by the process, this means that testers can be confident they have seen every system condition relevant to the coverage criteria. In this talk, I will describe this approach to automated test case generation and illustrate its utility with a simple example. I will then describe how this approach could be extended to account for different dimensions of human cognitive performance and emerging challenges in human-autonomy interaction.

Inherent system processes, restrictions on collection, or cost may impact the practical execution of an operational test. This study presents the use of blocking and split-plot designs when complete randomization is not feasible in operational test. Specifically, the USAF B-52 Radar Modernization Program test design is used to present tradeoffs of different design choices and the impacts of those choices on cost, operational relevance, and analytical rigor.

Inherent system processes, restrictions on collection, or cost may impact the practical execution of an operational test. This study presents the use of blocking and split-plot designs when complete randomization is not feasible in operational test. Specifically, the USAF B-52 Radar Modernization Program test design is used to present tradeoffs of different design choices and the impacts of those choices on cost, operational relevance, and analytical rigor.

Co-authors: Adam L. Pintar, Blaza Toman, and Dennis Leber. A task of the Domestic Nuclear Detection Office (DNDO) is the evaluation of radiation and nuclear (rad/nuc) detection systems used to detect and identify illicit rad/nuc materials. To obtain estimated system performance measures, such as probability of detection, and to determine system acceptability, the DNDO sometimes conduct large scale field tests of these systems at great cost. Typically, non adaptive designs are employed where each rad/nuc test source is presented to each system under test a predetermined and fixed number of times. This approach can lead to unnecessary cost if the system is clearly acceptable or unacceptable. In this presentation, an adaptive design with Bayesian decision theoretic foundations is discussed as an alternative to, and contrasted with, the more common single stage design. Although the basis of the method is Bayesian decision theory, designs may be tuned to have desirable type I and II error rates. While the focus of the presentation is a specific DNDO example, the method is applicable widely. Further, since constructing the designs is somewhat compute intensive, software in the form of an R package will be shown and is available upon request.

A challenging aspect of a system reliability assessment is integrating multiple sources of information, including component, subsystem, and full-system data, previous test data, or subject matter expert opinion. A powerful feature of Bayesian analyses is the ability to combine these multiple sources of data and variability in an informed way to perform statistical inference. This feature is particularly valuable in assessing system reliability where testing is limited and only a small number (or no failures at all) are observed. The F-35 is DoD’s largest program; approximately one-third of the operations and sustainment cost is attributed to the cost of spare parts and the removal, replacement, and repair of components. The failure rate of those components is the driving parameter for a significant portion of the sustainment cost, and yet for many of these components, poor estimates of the failure rate exist. For many programs, the contractor produces estimates of component failure rates, based on engineering analysis and legacy systems with similar parts. While these are useful, the actual removal rates can provide a more accurate estimate of the removal and replacement rates the program anticipates to experience in future years. In this presentation, we show how we applied a Bayesian analysis to combine the engineering reliability estimates with the actual failure data to overcome the problems of cases where few data exist. Our technique is broadly applicable to any program where multiple sources of reliability information need be combined for the best estimation of component failure rates and ultimately sustainment costs.

The application opportunities for behavioral analytics in the cybersecurity space are based upon simple realities. 1. The great majority of breaches across all cybersecurity venues is due to human choices and human error. 2. With communication and information technologies making for rapid availability of data, as well as behavioral strategies of bad actors getting cleverer, there is need for expanded perspectives in cybersecurity prevention. 3. Internally-focused paradigms must now be explored that place endogenous protection from security threats as an important focus and integral dimension of cybersecurity prevention. The development of cybersecurity monitoring metrics and tools as well as the creation of intrusion prevention standards and policies should always include an understanding of the underlying drivers of human behavior. As temptation follows available paths, cyber-attacks follow technology, business models, and behavioral habits. The human element will always be the most significant part in the anatomy of any final decision. Choice options – from input, to judgement, to prediction, to action – need to be better understood for their relevance to cybersecurity work. Behavioral Performance Indexes harness data about aggregate human participation in an active system, helping to capture some of the detail and nuances of this critically important dimension of cybersecurity.

The NASA Big Data, Big Think team jump-starts coordination, strategy, and progress for NASA applications of Big Data Analytics techniques, fosters collaboration and teamwork among centers and improves agency-wide understanding of Big Data research techniques & technologies and their application to NASA mission domains. The effort brings the Agency’s Big Data community together and helps define near term projects and leverages expertise throughout the agency. This presentation will share examples of Big Data activities from the Agency and discuss knowledge areas and experiences, including data management, data analytics and visualization.

Spectrograms (i.e., squared magnitude of short-time Fourier transform) are commonly used as features to classify audio signals in the same way that social media companies (e.g., Google, Facebook, Yahoo) use images to classify or automatically tag people in photos. However, a serious problem arises when using spectrograms to classify acoustic signals, in that the user must choose the input parameters (hyperparameters), and such choices can have a drastic effect on the accuracy of the resulting classifier. Further, considering all possible combinations of the hyperparameters is a computationally intractable problem. In this study, we simplify the problem making it computationally tractable, explore the utility of response surface methods for sampling the hyperparameter space, and find that response surface methods are a computationally efficient means of identifying the hyperparameter combinations that are likely to give the best classification results.

Helicopters serve a number of useful roles within the community; however, community acceptance of helicopter operations is often limited by the resulting noise. Because the noise characteristics of helicopters depend strongly on the operating condition of the vehicle, effective noise abatement procedures can be developed for a particular helicopter type, but only when the noisy regions of the operating envelope are identified. NASA Langley Research Center—often in collaboration with other US Government agencies, industry, and academia—has conducted noise measurements for a wide variety of helicopter types, from light commercial helicopters to heavy military utility helicopters. While this database is expansive, it covers only a fraction of helicopter types in current commercial and military service and was measured under a limited set of ambient conditions and vehicle configurations. This talk will describe a new “universal” helicopter noise model suitable for planning helicopter noise abatement procedures. Modern machine learning techniques will be combined with the principle of nondimensionalization and applied to NASA’s helicopter noise data in order to develop a model capable of estimating the noisy operating states of any conventional helicopter under any specific ambient conditions and vehicle configurations.

Model Validation for Simulations of CVN-78 Sortie Generation As part of the test planning process, IDA is examining flight operations on the Navy’s newest carrier, CVN-78. The analysis uses a model, the IDA Virtual Carrier Model (IVCM), to examine sortie generation rates and whether aircraft can complete missions on time. Before using IVCM, it must be validated. However, CVN-78 has not been delivered to the Navy, and data from actual operations are to validate the model. Consequently, we will validate IVCM by comparing it to another model. This is a reasonable approach when a model is used in general analyses such as test planning, but is not acceptable when a model is used in the assessment of system effectiveness and suitability. The presentation examines the use of various statistical tools – Wilcoxon Rank Sum Test, Kolmogorov-Smirnov Test, and lognormal regression – to examine whether the results from two models provide similar results and to quantify the magnitude of any differences. From the analysis, IDA concluded that locations and distribution shapes are consistent, and that the differences between the models are less than 15 percent, which is acceptable for test planning.

Co-Authors: Sean A. Commo, Ph.D., P.E. and Peter A. Parker, Ph.D., P.E. NASA Langley Research Center, Hampton, Virginia, USA Austin D. Overmeyer, Philip E. Tanner, and Preston B. Martin, Ph.D. U.S. Army Research, Development, and Engineering Command, Hampton, Virginia, USA. The application of statistical engineering to helicopter wind-tunnel testing was explored during two powered rotor entries. The U.S. Army Aviation Development Directorate Joint Research Program Office and the NASA Revolutionary Vertical Lift Project performed these tests jointly at the NASA Langley Research Center. Both entries were conducted in the 14- by 22-Foot Subsonic Tunnel with a small segment of the overall tests devoted to developing case studies of a statistical engineering approach. Data collected during each entry were used to estimate response surface models characterizing vehicle performance, a novel contribution of statistical engineering applied to powered rotor-wing testing. Additionally, a 16- to 47-times reduction in the number of data points required was estimated when comparing a statistically-engineered approach to a conventional one-factor-at-a-time approach.

The fundamental principles of experiment design are factorization, replication, randomization, and local control of error. In many industries, however, departure from these principles is commonplace. Often in our experiments complete randomization is not feasible because the factor level settings are hard, impractical, or inconvenient to change or the resources available to execute under homogeneous conditions are limited. These restrictions in randomization lead to split-plot experiments. We are also often interested in fitting second-order models leading to second-order split-plot experiments. Although response surface methodology has grown tremendously since 1951, the lack of alternatives for second-order split-plots remains largely unexplored. The literature and textbooks offer limited examples and provide guidelines that often are too general. This deficit of information leaves practitioners ill prepared to face the many roadblocks associated with these types of designs. This presentation provides practical strategies to help practitioners in dealing with second-order split-plot and by extension, split-split-plot experiments, including an innovative approach for the construction of a response surface design referred to as second-order sub-array Cartesian product split-plot design. This new type of design, which is an alternative to other classes of split-plot designs that are currently in use in defense and industrial applications, is economical, has a low prediction variance of the regression coefficients, and low aliasing between model terms. Based on an assessment using well accepted key design evaluation criterion, second-order sub-array Cartesian product split-plot designs perform as well as historical designs that have been considered standards up to this point.

Binomial metrics like probability-to-detect or probability-to-hit typically provide operationally meaningful and easy to interpret test outcomes. However, they are information poor metrics and extremely expensive to test. The standard power calculations to size a test employ hypothesis tests, which typically result in many tens to hundreds of runs. In addition to being expensive, the test is most likely inadequate for characterizing performance over a variety of conditions due to the inherently large statistical uncertainties associated with binomial metrics. A solution is to convert to a continuous variable, such as miss distance or time-to-detect. The common objection to switching to a continuous variable is that the hit/miss or detect/non-detect binomial information is lost, when the fraction of misses/no-detects is often the most important aspect of characterizing system performance. Furthermore, the new continuous metric appears to no longer be connected to the requirements document, which was stated in terms of a probability. These difficulties can be overcome with the use of censored data analysis. This presentation will illustrate the concepts and benefits of this approach, and will illustrate a simple analysis with data, including power calculations to show the cost savings for employing the methodology.

Analysis-based means of compliance for airplane and engine certification, commonly known as “Certification by Analysis” (CbA), provides a strong motivation for the development and maturation of current and future flight and engine modeling technology. The most obvious benefit of CbA is streamlined product certification testing programs at lower cost while maintaining equivalent levels of safety. The current state of technologies and processes for analysis is not sufficient to adequately address most aspects of CbA today, and concerted efforts to drastically improve analysis capability are required to fully bring the benefits of CbA to fruition. While the short-term cost and schedule benefits of reduced flight and engine testing are clearly visible, the fidelity of analysis capability required to realize CbA across a much larger percentage of product certification is not yet sufficient.  Higher-fidelity analysis can help reduce the product development cycle and avoid costly and unpredictable performance and operability surprises that sometimes happen late in the development cycle. Perhaps the greatest long-term value afforded by CbA is the potential to accelerate the introduction of more aerodynamically and environmentally efficient products to market, benefitting not just manufacturers, but also airlines, passengers, and the environment. A far-reaching vision for CbA has been constructed to offer guidance in developing lofty yet realizable expectations regarding technology development and maturity through stakeholder involvement. This vision is composed of the following four elements: The ability to numerically simulate the integrated system performance and response of full-scale airplane and engine configurations in an accurate, robust, and computationally efficient manner. The development of quantified flight and engine modeling uncertainties to establish appropriate confidence in the use of numerical analysis for certification. The rigorous validation of flight and engine modeling capabilities against full-scale data from critical airplane and engine testing. The use of flight and engine modeling to enable Certification by Simulation. Key technical challenges include the ability to accurately predict airplane and engine performance for a single discipline, the robust and efficient integration of multiple disciplines, and the appropriate modeling of system-level assessment. Current modeling methods lack the capability to adequately model conditions that exist at the edges of the operating envelope where the majority of certification testing generally takes place.  Additionally, large-scale engine or airplane multidisciplinary integration has not matured to the level where it can be reliably used to efficiently model the intricate interactions that exist in current or future aerospace products. Logistical concerns center primarily on the future High Performance Computing capability needed to perform the large number of computationally intensive simulations needed for CbA. Complex, time-dependent, multidisciplinary analyses will require a computing capacity increase several orders of magnitude greater than is currently available. Developing methods to ensure credible simulation results is critically important for regulatory acceptance of CbA. Confidence in analysis methodology and solutions is examined so that application validation cases can be properly identified. Other means of measuring confidence such as uncertainty quantification and “validation-domain” approaches may increase the credibility and trust in the predictions. Certification by Analysis is a challenging long-term endeavor that will motivate many areas of simulation technology development, while driving the potential to decrease cost, improve safety, and improve airplane and engine efficiency. Requirements to satisfy certification regulations provide a measurable definition for the types of analytical capabilities required for success. There is general optimism that CbA is a goal that can be achieved, and that a significant amount of flight testing can be reduced in the next few decades.