Proposed Testing Strategy Research Articles

How to implement signed-rank wilcox.test() type procedures when a center of symmetry is unknown

The aim is twofold: (1) to indicate that the one-sample Wilcoxon signed rank test cannot be used directly when a center of symmetry is unknown; and (2) to propose and examine correct schemes for applying the Wilcoxon signed rank test with an estimated center of symmetry. It turns out that the Wilcoxon signed rank test and the sign test for symmetry do not provide valued outputs, when unknown centers of symmetry are estimated using underlying data. In such scenarios, these tests are not null-distribution-free and break down completely even based on samples with large numbers of observations. Theoretical propositions are shown to propose a simple correction of the corresponding R built-in function, employing p-value-based procedures. To perform the proposed algorithms, we develop new customized procedures for estimating the integrated squares of densities, probability weighted moments and special values of density functions. It is shown that the proposed testing strategies have Type I error rates under good control as well as exhibit high and stable power characteristics.The proposed algorithms can be applied for modifying Wilcoxon tests type procedures in different statistical software.

Strategy for Vacuum Insulation Tests of MITICA 1 MV Electrostatic Accelerator

The electrical insulation of the Megavolt ITER Injector and Concept Advancement (MITICA) beam source (BS) at 1 MV in vacuum is a challenging issue, which could not be fully addressed so far on the basis of experimental results and of theoretical models available in literature. A specific high-voltage (HV) test campaign is being prepared to validate and optimize the voltage holding capability of the BS insulation under realistic conditions, using full-size mockup electrodes reproducing in detail the geometry of the BS and accelerator. The proposed test strategy will address both the single-gap and the multistage insulation, so as to obtain a verification of voltage holding at 1 MV before the installation of the real components. This approach is intended to reduce the risk related to the HV insulation at 1 MV and, if necessary, to allow the development of effective corrections. In this article, the test motivations and requirements are defined, and the electrode implementation and diagnostic setup are described. Finally, the test configurations and the experimental procedure are discussed.

Experimental Verification of a New Oscillation-based Test Algorithm for Analog Circuits

Oscillation-based test algorithm has been proposed and verified experimentally as an alternative to the specification--based test of analog circuits. Active filters are transformed to oscillators using nonlinear feedback, realized with a Schmitt trigger. Faults are detected based on the deviation of the oscillation frequency outside the tolerance band due to the variation of different circuit components under test. This proposed technique ensures high test precision due to the processing of the oscillation frequency with the help of a purely digital circuit. Undetectable ranges of parametric faults of circuit components have been identified by simulation with Cadence virtuoso using the 0.18 µm CMOS technology. Then, practical circuits of second order Butterworth Low Pass Filter and Sallen-Key Band Pass Filter have been tested experimentally. Experimental results ensure high fault coverage of the proposed test strategy.

Testing of in-memory-computing memories with 8 T SRAMs

In-memory-computing (IMC) architecture has been proposed as an alternative to cope with the memory wall of von-Neumann computing architecture. The IMC architecture embeds logic into the memory array to reduce the data transfer between the processor and memory. An IMC memory can be operated in memory mode and computing mode, which increases the test complexity. Thus, the IMC memory need to be tested in memory mode and computing mode. In this paper, we propose a test strategy for IMC 8 T SRAMs with NAND and NOR logic operations. Possible functional faults caused by the isolated read port of the 8 T SRAM cell are analyzed. A 12N March C−8 test algorithm is proposed to cover functional faults in memory mode and process variation-induced faults in computing mode of an N-bit IMC 8 T SRAM. Extendibility of the proposed test strategy for 8 T SRAMs and multiple operands is shown as well.

Screening multi-dimensional heterogeneous populations for infectious diseases under scarce testing resources, with application to COVID-19.

Testing provides essential information for managing infectious disease outbreaks, such as the COVID‐19 pandemic. When testing resources are scarce, an important managerial decision is who to test. This decision is compounded by the fact that potential testing subjects are heterogeneous in multiple dimensions that are important to consider, including their likelihood of being disease‐positive, and how much potential harm would be averted through testing and the subsequent interventions. To increase testing coverage, pooled testing can be utilized, but this comes at a cost of increased false‐negatives when the test is imperfect. Then, the decision problem is to partition the heterogeneous testing population into three mutually exclusive sets: those to be individually tested, those to be pool tested, and those not to be tested. Additionally, the subjects to be pool tested must be further partitioned into testing pools, potentially containing different numbers of subjects. The objectives include the minimization of harm (through detection and mitigation) or maximization of testing coverage. We develop data‐driven optimization models and algorithms to design pooled testing strategies, and show, via a COVID‐19 contact tracing case study, that the proposed testing strategies can substantially outperform the current practice used for COVID‐19 contact tracing (individually testing those contacts with symptoms). Our results demonstrate the substantial benefits of optimizing the testing design, while considering the multiple dimensions of population heterogeneity and the limited testing capacity.

A Nonintrusive Machine Learning-Based Test Methodology for Millimeter-Wave Integrated Circuits

In this article, we leverage the power of machine learning algorithms to propose a test methodology for millimeter-wave (mm-wave) integrated circuits. The proposed test strategy is based on identifying the main process degradation mechanisms in a particular device under test (DUT) and then designing dedicated process monitor circuits to characterize this degradation and infer the DUT performance. The resulting process monitors do not load or couple to any of the DUT nodes, and the methodology can be adapted to any mm-wave device without complex codesign. The proposed test methodology is illustrated on a set of 21 fabricated samples of a 65-GHz PA designed in STMicroelectronics 55-nm CMOS technology.

Devising a Tier-based Skin Sensitisation Screening Strategy for Personal Care and Cosmetic Products.

Concerns regarding the use of potential skin sensitisers in personal care and cosmetic products continue to grow. The goal of this study was to develop a proof-of-concept tier-based screening strategy for the assessment of skin sensitisation potential by using non-animal methodologies. As a case example, this screening framework was applied to three WEN® by Chaz Dean cleansing conditioners. The first tier of testing utilised the Organisation for Economic Co-operation and Development (OECD) Quantitative Structure Activity Relationship Toolbox profiler to evaluate the skin sensitisation potential of individual ingredients within the formulation; a literature review was performed on the substances that generated in silico alerts. Tier 2 testing utilised the OECD in chemico Test Guideline (TG) 442C to evaluate these substances. Tier 3 testing adapted OECD TG442C to evaluate the formulated product. The literature review on the four substances that generated in silico alerts revealed that they were not sensitising at the concentrations reported in the formulated products. Tier 2 testing demonstrated that these substances were not sensitising at the concentrations tested. Finally, Tier 3 testing revealed that the evaluated cleansing conditioners had low mean percentage peptide depletion at the concentrations tested. Together, the results obtained suggest that the products tested are unlikely to induce skin sensitisation under the given experimental conditions. These findings are in agreement with other in vitro and clinical studies. The proposed tier-based testing approach may be used as a conceptual framework for the prospective safety screening of other personal care and cosmetic products. However, to establish the validity of the proposed testing strategy, further studies must be performed, including comparisons with established models.

Design of an Oscillation-Based BIST System for Active Analog Integrated Filters in 0.18 µm CMOS

In this paper, an oscillation-based built-in self-test system for active an analog integrated circuit is presented. This built-in self-test system was used to detect catastrophic and parametric faults, introduced during chip manufacturing. As circuits under test (CUT), second-order Sallen-Key, Akerberg-Mossberg and Tow-Thomas biquad filters were designed. The proposed test hardware detects parametric and catastrophic faults on changeable limits. The influence of both oscillation and test hardware on fault detection limits were investigated and analyzed. The proposed oscillation based self-test system was designed and simulated in 0.18 µm complementary metal-oxide semiconductor (CMOS) technology. Due to the easiness of implementation and configuration for testing of different active analog filters, such self-test systems can be effectively used in modern integrated circuits, made of a large number of devices and circuits, such as the multi-standard transceivers used in the core hardware of software-defined radios. Using the proposed test strategy, the fault tolerance limits for catastrophic faults varied from 96% to 100% for all injected faults in different structures of low pass filters (LPF). The detection range of parametric faults of passive components’ nominal value, depending on the used structure of the filter, did not exceed –0.74% – 0.72% in case of Sallen-Key, –3.31% – 1.00% in case of Akerberg-Mossberg and –2.39% – 1.44% in case of Tow-Thomas LPF.

A Digital Testing Strategy for Characterizing an Analog Circuit Block

This paper presents a digital testing strategy for characterizing an analog circuit block. The operational amplifier (op amp) is evaluated due to its wide application in electronic circuits and systems. In the proposed strategy, the op amp device under test (DUT) is configured to respond to a testing pulse, and the associated output is digitized by a digital buffer to reduce the high cost of generating a high-frequency clock. The testing procedure is divided into two modes to estimate the reference slew rate and then to evaluate the practical slew rate to moderate the difficulty of designing a digital buffer that has a highly precise delay time. The testing concept, accuracy, time, and hardware are also comprehensively investigated to describe the proposed testing strategy. The digital compatibility, the simplicity, and the testing capability of the high-performance op amp are the main advantages of the proposed testing strategy. Easily available discrete devices were experimentally employed to verify the functionality of the proposed testing strategy. An integrated application to test the op amp DUT embedded in a second-order Sallen–Key low-pass filter was simulated with the HSPICE tool to verify the testing feasibility and the effectiveness of the proposed strategy.

Tuberculosis and the traveller: evaluating and reducing risk through travel consultation.

Although the last 10 years have seen a slow decline in global tuberculosis (TB) incidence, it remains one of the most significant infectious diseases worldwide, with an estimated 9.6 million new cases and 1.5 million deaths in 2014. The consequences of contracting TB can be significant for the individual, with extended treatment requirements, risk of long-term health consequences and the possibility of transmitting infection to others among the complications of disease. This review article discusses the risk of TB infection as a result of international travel including evaluation of risk, risk reduction and a proposed testing strategy for travel-related TB infection. A review of the relevant literature combined with expert opinion was used to formulate this article. The global TB epidemic is varied and dynamic, including changing patterns of both drug sensitive and drug resistant disease. The annual incidence of TB in individual countries such as South Africa may be greater than 800/100,000, while multidrug resistance is found in up to 19% of new cases in the Russian Federation. Recent surveys of traveller risk are presented for short and long-term travellers to various countries and settings. Overall, risk to travelers is low, with rates of acquiring latent TB less than 1% per travel year for most settings. However, detailed travel evaluation is necessary to evaluate individual risk. Travellers with immunosuppressive conditions are at high risk for progression to active disease if infected, and should have special consideration in travel consultation. It is important for practitioners giving advice regarding tuberculosis risk and travel to access up-to-date information regarding local conditions. This article provides an approach to assessment and management of TB in travellers, including a guide to pre- and post-travel evaluation, testing and vaccination.

A test for detecting etiologic heterogeneity in epidemiological studies

Current statistical methods for analyzing epidemiological data with disease subtype information allow us to acquire knowledge not only for risk factor-disease subtype association but also, on a more profound account, heterogeneity in these associations by multiple disease characteristics (so-called etiologic heterogeneity of the disease). Current interest, particularly in cancer epidemiology, lies in obtaining a valid p-value for testing the hypothesis whether a particular cancer is etiologically heterogeneous. We consider the two-stage logistic regression model along with pseudo-conditional likelihood estimation method and design a testing strategy based on Rao's score test. An extensive Monte Carlo simulation study is carried out, false discovery rate and statistical power of the suggested test are investigated. Simulation results indicate that applying the proposed testing strategy, even a small degree of true etiologic heterogeneity can be recovered with a large statistical power from the sampled data. The strategy is then applied on a breast cancer data set to illustrate its use in practice where there are multiple risk factors and multiple disease characteristics of simultaneous concern.

Frequentist Evaluation of Small DSGE Models

This article proposes a new evaluation approach for the class of small-scale “hybrid” new Keynesian dynamic stochastic general equilibrium (NK-DSGE) models typically used in monetary policy and business cycle analysis. The empirical assessment of the NK-DSGE model is based on a conditional sequence of likelihood-based tests conducted in a vector autoregressive (VAR) system, in which both the low- and high-frequency implications of the model are addressed in a coherent framework. If the low-frequency behavior of the original time series of the model can be approximated by nonstationary processes, stationarity must be imposed by removing the stochastic trends. This gives rise to a set of recoverable unit roots/cointegration restrictions, in addition to the short-run cross-equation restrictions. The procedure is based on the sequence “LR1→LR2→LR3,” where LR1 is the cointegration rank test, LR2 is the cointegration matrix test, and LR3 is the cross-equation restrictions test: LR2 is computed conditional on LR1 and LR3 is computed conditional on LR2. The Type I errors of the three tests are set consistently with a prefixed overall nominal significance level. A bootstrap analog of the testing strategy is proposed in small samples. We show that the information stemming from the individual tests can be used constructively to uncover which features of the data are not captured by the theoretical model and thus to rectify, when possible, the specification. We investigate the empirical size properties of the proposed testing strategy by a Monte Carlo experiment and show the empirical usefulness of our approach by estimating and testing a monetary business cycle NK-DSGE model using U.S. quarterly data. Supplementary materials for this article are available online.

Case study to illustrate an approach for detecting contamination and impurities in pesticide formulations.

Counterfeit pesticides threaten public health, food trade, and the environment. The present work draws attention to the importance of regular monitoring of impurities in formulated pesticide products. General screening revealed the presence of carbaryl as a contaminant in a copper oxychloride formulated product. In this paper, as a case study, a liquid chromatographic diode array-mass spectrometric method developed for general screening of pesticide products and quantitative determination of carbaryl together with its validation is presented. The proposed testing strategy is considered suitable for use as a general approach for testing organic contaminants and impurities in solid pesticide formulations.

A testing strategy to predict risk for drug-induced liver injury in humans using high-content screen assays and the 'rule-of-two' model.

Drug-induced liver injury (DILI) is a major cause of drug failures in both the preclinical and clinical phase. Consequently, improving prediction of DILI at an early stage of drug discovery will reduce the potential failures in the subsequent drug development program. In this regard, high-content screening (HCS) assays are considered as a promising strategy for the study of DILI; however, the predictive performance of HCS assays is frequently insufficient. In the present study, a new testing strategy was developed to improve DILI prediction by employing in vitro assays that was combined with the RO2 model (i.e., 'rule-of-two' defined by daily dose ≥100 mg/day & logP ≥3). The RO2 model was derived from the observation that high daily doses and lipophilicity of an oral medication were associated with significant DILI risk in humans. In the developed testing strategy, the RO2 model was used for the rational selection of candidates for HCS assays, and only the negatives predicted by the RO2 model were further investigated by HCS. Subsequently, the effects of drug treatment on cell loss, nuclear size, DNA damage/fragmentation, apoptosis, lysosomal mass, mitochondrial membrane potential, and steatosis were studied in cultures of primary rat hepatocytes. Using a set of 70 drugs with clear evidence of clinically relevant DILI, the testing strategy improved the accuracies by 10 % and reduced the number of drugs requiring experimental assessment by approximately 20 %, as compared to the HCS assay alone. Moreover, the testing strategy was further validated by including published data (Cosgrove et al. in Toxicol Appl Pharmacol 237:317-330, 2009) on drug-cytokine-induced hepatotoxicity, which improved the accuracies by 7 %. Taken collectively, the proposed testing strategy can significantly improve the prediction of in vitro assays for detecting DILI liability in an early drug discovery phase.

Pooled Association Tests for Rare Genetic Variants: A Review and Some New Results

In the search for genetic factors that are associated with complex heritable human traits, considerable attention is now being focused on rare variants that individually have small effects. In response, numerous recent papers have proposed testing strategies to assess association between a group of rare variants and a trait, with competing claims about the performance of various tests. The power of a given test in fact depends on the nature of any association and on the rareness of the variants in question. We review such tests within a general framework that covers a wide range of genetic models and types of data. We study the performance of specific tests through exact or asymptotic power formulas and through novel simulation studies of over 10,000 different models. The tests considered are also applied to real sequence data from the 1000 Genomes project and provided by the GAW17. We recommend a testing strategy, but our results show that power to detect association in plausible genetic scenarios is low for studies of medium size unless a high proportion of the chosen variants are causal. Consequently, considerable attention must be given to relevant biological information that can guide the selection of variants for testing.

Moving Towards Agile Testing Strategies

Testing is a vital activity for delivering a high qualitysoftware product to the customers. Often testing accounts for more project effort and time than any other software development activities. Traditional software development process models are being used for long time in software development. Recently, the software development in the industry is moving towards agile due to the advantages provided by the agile development process. One of the main advantages of agile software development process is delivering the high quality software to the customers in shorter intervals. Another important advantage is, the agile process models embrace the changes in requirements at any stage of software development. Due to these advantages, software industry is showing interest in software development using agile process models. One of the agile process models which is being used in the software industry is, the “scrum”. Since testing plays a major role in the success of the product, it is given a lot of importance in software development. Testing strategies for conventional process models are well established, but these strategies are not directly applicable to agile testing without modifications and changes. One of the important current research areas is the agile software testing strategies. The main objective for any agile testing strategy is to reduce the testing time and at the same time ensuring the software quality. In this paper, a strategy for agile testing in the scrum software development environment is proposed and presented. The sprint activities which form the context for the proposed testing strategy are also proposed. The tools which are helpful for automation which is part of the strategy are presented. The advantages of the proposed strategy are highlighted. Case study which used the proposed strategy is presented, it indicated that the number of bugs reported by customer reduced significantly in scrum agile development using the proposed testing strategy.

‘Location, Location, Location’: a spatial approach for rare variant analysis and an application to a study on non-syndromic cleft lip with or without cleft palate

Motivation: For the analysis of rare variants in sequence data, numerous approaches have been suggested. Fixed and flexible threshold approaches collapse the rare variant information of a genomic region into a test statistic with reduced dimensionality. Alternatively, the rare variant information can be combined in statistical frameworks that are based on suitable regression models, machine learning, etc. Although the existing approaches provide powerful tests that can incorporate information on allele frequencies and prior biological knowledge, differences in the spatial clustering of rare variants between cases and controls cannot be incorporated. Based on the assumption that deleterious variants and protective variants cluster or occur in different parts of the genomic region of interest, we propose a testing strategy for rare variants that builds on spatial cluster methodology and that guides the identification of the biological relevant segments of the region. Our approach does not require any assumption about the directions of the genetic effects.Results: In simulation studies, we assess the power of the clustering approach and compare it with existing methodology. Our simulation results suggest that the clustering approach for rare variants is well powered, even in situations that are ideal for standard methods. The efficiency of our spatial clustering approach is not affected by the presence of rare variants that have opposite effect size directions. An application to a sequencing study for non-syndromic cleft lip with or without cleft palate (NSCL/P) demonstrates its practical relevance. The proposed testing strategy is applied to a genomic region on chromosome 15q13.3 that was implicated in NSCL/P etiology in a previous genome-wide association study, and its results are compared with standard approaches.Availability: Source code and documentation for the implementation in R will be provided online. Currently, the R-implementation only supports genotype data. We currently are working on an extension for VCF files.Contact: heide.fier@googlemail.com

Kth-Aggressor Fault (KAF)-based Thru-Silicon-Via Interconnect Built-In Self-Test and Diagnosis

Three-dimensional (3D) integration is a key technology for systems whose performance and power requirements cannot be achieved by traditional silicon technologies. 3D chips consist of two or more stacked silicon dies connected by short inter-die wires called Thru-Silicon-Vias (TSVs). Despite its potential, the poor reliability and yield, thermal management and testing issues remain major challenges of 3D integration. We address the TSV interconnect test challenge of 3D chips by using Interconnect Built-In Self-Test (IBIST) techniques. The proposed test strategy must sensitize structural faults like opens and shorts, and delay faults due to crosstalk. A possible approach is the well-known Maximum Aggressor Fault (MAF) model. Unfortunately, this model is too conservative and it leads to long test sequences and non-negligible hardware costs. Therefore, we present an alternative solution: the Kth-Aggressor Fault (KAF) model. In our model, aggressors of victim wires are neighboring wires within an optimized distance order K. The aggressor order K is technology-dependent and is determined such that the test times are minimal and the fault coverage is maximal. KAF-based IBIST implementation targeting TSV tests occupies three times less area than similar MAF-/marching-based implementations. We also propose a reconfigurable KAF-based IBIST implementation where tests can be performed using different aggressor orders K. Although the reconfigurable IBIST area is significant, interconnect tests during system lifetime can be performed using lower aggressor orders, reducing test duration and improving TSV availability.

A Consistency-Adjusted Strategy for Accommodating an Underpowered Primary Endpoint

A clinical trial might involve more than one clinically important endpoint, each of which can characterize the treatment effect of the experimental drug under investigation. Underlying the concept of using such endpoints interchangeably to establish an efficacy claim, or pooling different endpoints to constitute a composite endpoint, is the assumption that findings from such endpoints are consistent with each other. While such an assumption about consistency of efficacy findings appears to be intuitive, it is seldom considered in the design and analysis literature of clinical trials with multiple endpoints. Failure to account for consistency of efficacy findings of two candidate endpoints to establish efficacy, at the design stage, has led to difficulties in interpreting study findings. This article presents a flexible testing strategy for accommodating findings of an alternative to the designated primary endpoint (or a subgroup) to support an efficacy claim. The method is built on the following two premises: (i) Efficacy findings of the designated primary endpoint, although nonsignificant, need to be supportive of those of the alternative endpoint, and (ii) the significance level allocated for testing the second endpoint is determined adaptively based on the magnitude of the p-value for the designated primary endpoint. The method takes into account the hierarchical ordering of the hypotheses tested and the correlation between the test statistics for the two endpoints to increase the chance of a positive trial. We discuss control of the type I error rate for the proposed test strategy and compare its power with that of other methods. In addition, we consider its application to two clinical trials.

Built-In Sensor for Signal Integrity Faults in Digital Interconnect Signals

Testing of signal integrity (SI) in current high-speed ICs, requires automatic test equipment test resources at the multigigahertz range, normally not available. Furthermore, for most internal nets of state-of-the-art ICs, external speed testing is not possible for the newest technologies. In this paper, on-chip testing for SI faults in digital interconnect signals, using built-in high speed monitors, is proposed. A coherent sampling scheme is used to capture the signal information. Two monitors to test SI violations are proposed: one for undershoots at the high logic level and the other for overshoots at the low logic level. The monitors are capable of detecting small noise pulses and have been extended to test sequentially more than one signal. The cost of the proposed strategy is analyzed in terms of area, delay penalization, and test time. The effects of clock jitter and process variations are analyzed. Experimental results obtained in designed and fabricated circuits show the feasibility of the proposed testing strategy. A good agreement appears between the theoretical analysis, simulation results, and the experimental measurements.