DATAWorks Sessions Archive

A strength of the Bayesian paradigm is that it allows for the explicit use of all available information—to include subject matter expert (SME) opinion and previous (possibly dissimilar) data. While frequentists are constrained to only including data in an analysis (that is to say, only including information that can be observed), Bayesians can easily consider both data and SME opinion, or any other related information that could be constructed. This can be accomplished through the development and use of priors. When prior development is done well, a Bayesian analysis will not only lead to more direct probabilistic statements about system performance, but can result in smaller standard errors around fitted values when compared to a frequentist approach. Furthermore, by quantifying the uncertainty surrounding a model parameter, through the construct of a prior, Bayesians are able to capture the uncertainty across a test space of consideration. This presentation develops a framework for thinking about how different priors can be used throughout the continuum of testing. In addition to types of priors, how priors can change or evolve across the continuum of testing—especially when a system changes (e.g., is modified or adjusted) during phases of testing—will be addressed. Priors that strive to provide no information (reference priors) will be discussed, and will build up to priors that contain available information (informative priors). Informative priors—both those based on institutional knowledge or summaries from databases, as well as those developed based on previous testing data—will be discussed, with a focus on how to consider previous data that is dissimilar in some way, relative to the current test event. What priors might be more common in various phases of testing, types of information that can be used in priors, and how priors evolve as information accumulates will all be discussed.

In the acquisition and testing world, data analysts repeatedly encounter certain categories of data, such as time or distance until an event (e.g., failure, alert, detection), binary outcomes (e.g., success/failure, hit/miss), and survey responses. Analysts need tools that enable them to produce quality and timely analyses of the data they acquire during testing. This poster presents four web-based apps that can analyze these types of data. The apps are designed to assist analysts and researchers with simple repeatable analysis tasks, such as building summary tables and plots for reports or briefings. Using software tools like these apps can increase reproducibility of results, timeliness of analysis and reporting, attractiveness and standardization of aesthetics in figures, and accuracy of results. The first app models reliability of a system or component by fitting parametric statistical distributions to time-to-failure data. The second app fits a logistic regression model to binary data with one or two independent continuous variables as predictors. The third calculates summary statistics and produces plots of groups of Likert-scale survey question responses. The fourth calculates the system usability scale (SUS) scores for SUS survey responses and enables the app user to plot scores versus an independent variable. These apps are available for public use on the Test Science Interactive Tools webpage https://new.testscience.org/interactive-tools/.

This paper presents an analysis of target location error (TLE) based on the Cox Ingersoll Ross (CIR) model. In brief, this model characterizes TLE as a function of range based the stochastic differential equation model dX(r) = a(b-X(r))dr + sigma *sqrt(X(r)) dW(r) where X(t) is TLE at range r, b is the long-term mean (terminal) of the TLE, a is the rate of reversion of X(r) to b, sigma is the process volatility, and W(t) is the standard Weiner process. Multiple flight test runs under the same conditions exhibit different realizations of the TLE process. This approach to TLE analysis models each flight test run as a realization the CIR process. Fitting a CIR model to multiple data runs then provides a characterization of the TLE system under test. This paper presents an example use of the CIR model. Maximum likelihood estimates of the parameters of the CIR model are found from a collection of TLE data runs. The resulting CIR model is then used to characterize overall system TLE performance as a function of range to the target as well as the asymptotic estimate of long-term TLE.

It is widely recognized that the complexity and resulting capabilities of autonomous systems created using machine learning methods, which we refer to as learning enabled autonomous systems (LEAS), pose new challenges to systems engineering test, evaluation, verification, and validation (TEVV) compared to their traditional counterparts. This presentation provides a preliminary attempt to map recently developed technical approaches in the assurance and TEVV of learning enabled autonomous systems (LEAS) literature to a traditional systems engineering v-model. This mapping categorizes such techniques into three main approaches: development, acquisition, and sustainment. This mapping reviews the latest techniques to develop safe, reliable, and resilient learning enabled autonomous systems, without recommending radical and impractical changes to existing systems engineering processes. By performing this mapping, we seek to assist acquisition professionals by (i) informing comprehensive test and evaluation planning, and (ii) objectively communicating risk to leaders. The inability to translate qualitative assessments to quantitative metrics which measure system performance hinder adoption. Without understanding the capabilities and limitations of existing assurance techniques, defining safety and performance requirements that are both clear and testable remains out of reach. We accompany recent literature reviews on autonomy assurance and TEVV by mapping such developments to distinct steps of a well known systems engineering model chosen due to its prevalence, namely the v-model. For three top-level lifecycle phases: development, acquisition, and sustainment, a section of the presentation has been dedicated to outlining recent technical developments for autonomy assurance. This representation helps identify where the latest methods for TEVV fit in the broader systems engineering process while also enabling systematic consideration of potential sources of defects, faults, and attacks. Note that we use the v-model only to assist the classification of where TEVV methods fit. This is not a recommendation to use a certain software development lifecycle over another.

Traditional methods to assess software characterize the defect detection process as a function of testing time or effort to quantify failure intensity and reliability. More recent innovations include models incorporating covariates that explain defect detection in terms of underlying test activities. These covariate models are elegant and only introduce a single additional parameter per testing activity. However, the model forms typically exhibit a high degree of non-linearity. Hence, stable and efficient model fitting methods are needed to enable widespread use by the software community, which often lacks mathematical expertise. To overcome this limitation, this poster presents Bayesian estimation methods for covariate models, including the specification of informed priors as well as confidence intervals for the mean value function and failure intensity, which often serves as a metric of software stability. The proposed approach is compared to traditional alternative such as maximum likelihood estimation. Our results indicate that Bayesian methods with informed priors converge most quickly and achieve the best model fits. Incorporating these methods into tools should therefore encourage widespread use of the models to quantitatively assess software.

STAT practitioners often find ourselves outsiders to the programs we assist. This session presents a case study that demonstrates some of the obstacles in communication of capabilities, purpose, and expectations that may arise due to approaching the project externally. Incremental value may open the door to greater collaboration in the future, and this presentation discusses potential solutions to provide greater benefit to testing programs in the face of obstacles that arise due to coming from outside the program team. DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. CLEARED on 5 Jan 2022. Case Number: 88ABW-2022-0002

In this talk we’ll focus on exploring the motivation for using cloud computing for Computational Fluid Dynamics (CFD) for Federal Government Test & Evaluation. Using examples from automotive, aerospace and manufacturing we’ll look at benchmarks for a number of CFD codes using CPUs (x86 & Arm) and GPUs and we’ll look at how the development of high-fidelity CFD e.g. WMLES, HRLES, is accelerating the need for access to large scale HPC. The onset of COVID-19 has also meant a large increase in the need for remote visualization with greater numbers of researchers and engineering needing to work from home. This has also accelerated the adoption of the same approaches needed towards the pre- and post-processing of peta/exa-scale CFD simulation and we’ll look at how these are more easily accessed via a cloud infrastructure. Finally, we’ll explore perspectives on integrating ML/AI into CFD workflows using data lakes from a range of sources and where the next decade may take us.