Evaluating Item Selection Methods for Adaptive Tests with Complex Content Constraints

Adaptive testing designs have become go-to methods for large-scale test administration due to their ability to provide more accurate scores with fewer items. In recent years, new designs have been introduced, such as on-the-fly multistage testing (OMST), that combine the advantages of the well-established computerized adaptive testing (CAT) and multistage testing (MST) designs. While adaptive testing has attracted a tremendous amount of research, most studies have used only one set of test specifications to constrain the content of the test. Through Monte Carlo simulation, this study evaluated the effectiveness of CAT, MST, and OMST under varying levels of test specification complexity. Specifically, the constrained item selection methods of the maximum priority index (MPI) and weighted penalty model (WPM) were examined in CAT and OMST while the normalized weighted absolute deviation heuristic (NWADH) was used to assemble MST forms. In addition to the complexity of the test specifications, the representation of each content category in the pool and on the test, size of the item pool, length of each stage, and number of preassembled MST difficulty levels were also varied. The performance of each test design was evaluated by three outcomes: content alignment, measurement precision, and test security. Results show that increasing the complexity of test specifications leads to worse content alignment across all test designs and item selection methods. The WPM item selection method performs better than the MPI and NWADH under increased constraint complexity. Moreover, CAT and OMST provide higher measurement precision than MST, especially for the large item pool. Finally, CAT is the most secure among the three test designs and the security of MST benefits most from the larger item pool

Dynamic Effects on Fatigue Life of Cement Treated Crushed Rock

Fatigue life prediction of cement treated crushed rock is not a well understood concept in pavement engineering. The complexity to understand fatigue response of pavement lies not only in the structural model or the defining criteria for measurement, but also includes the testing regime to be adopted. Despite the well established testing methodologies for asphalt, minimal literature and standardised laboratory regimes exists for cemented basecourse. Fatigue testing of these materials is complicated by a multitude of variables that has to be considered in order to provide meaningful and representative data for design. Recent studies have been undertaken in Australia recently to characterise the fatigue phenomenon using a four point bending test setup by Austroad. Nevertheless, the loading frequency on fatigue life has not been addressed explicitly. A laboratory investigation to assess the loading frequency during pavement testing is undertaken. The paper presents the challenges and resultsachieved from test

Slosh Baffle Design and Test for Spherical Liquid Oxygen and Liquid Methane Propellant Tank for a Lander

A Vertical Test Bed (VTB) is being developed to investigate exploration technologies with earth-based landing trajectories. During this activity, a concern emerged that the VTB, with large liquid tanks, could experience unstable slosh interaction between the propellant fluid motion and the control system, leading to an investigation of slosh characteristics of the VTB. As such, slosh modeling, analysis and testing were performed, that both verified models and lead to the conclusion that baffles would be required for the full-scale vehicle. Follow-on design and testing supported development of these baffles and measurement of their performance. The majority of the tests conducted, including both subscale and full, involved the use of clear tanks containing water as a reasonable substitute for the cryogenic propellants, though a few tests involved the actual liquid oxygen and methane. Along the way, some unique test and data recording methods were employed to reduce testing complexity and cost

System Considerations for Establishing PreLaunch checkout Effectiveness

Factors contributing to the effectiveness of prelaunch testing are examined from a systems viewpoint. The complexity of manned space vehicles increases the quantity of test data that must be evaluated before launch can take place. The effect of these factors on prelaunch checkout is to place greater emphasis in the care of establishing: (1) accuracy and error budgets, (2) test techniques and equipment design, and (3) methods, plans and procedures for carrying out the prelaunch test program. By defining checkout effectiveness in terms of probabilities of undetected failures and false alarms at time of launch, the constraints on the above categories can be shown in numerical terms. Interrelationships between test intervals, percentage of system tested, measurement accuracy, stimulus and measurement techniques, and procedures in use of the test system are developed

Developmental Lead and/or Prenatal Stress Exposures Followed by Different Types of Behavioral Experience Result in the Divergence of Brain Epigenetic Profiles in a Sex, Brain Region, and Time-Dependent Manner: Implications for Neurotoxicology.

Over a lifetime, early developmental exposures to neurocognitive risk factors, such as lead (Pb) exposures and prenatal stress (PS), will be followed by multiple varied behavioral experiences. Pb, PS and behavioral experience can each influence brain epigenetic profiles. Our recent studies show a greater level of complexity, however, as all three factors interact within each sex to generate differential adult variation in global post-translational histone modifications (PTHMs), which may result in fundamentally different consequences for life-long learning and behavioral function. We have reported that PTHM profiles differ by sex, brain region and time point of measurement following developmental exposures to Pb±PS, resulting in different profiles for each unique combination of these parameters. Imposing differing behavioral experience following developmental Pb±PS results in additional divergence of PTHM profiles, again in a sex, brain region and time-dependent manner, further increasing complexity. Such findings underscore the need to link highly localized and variable epigenetic changes along single genes to the highly-integrated brain functional connectome that is ultimately responsible for governing behavioral function. Here we advance the idea that increased understanding may be achieved through iterative reductionist and holistic approaches. Implications for experimental design of animal studies of developmental exposures to neurotoxicants include the necessity of a \u27no behavioral experience\u27 group, given that epigenetic changes in response to behavioral testing can confound effects of the neurotoxicant itself. They also suggest the potential utility of the inclusion of salient behavioral experiences as a potential effect modifier in epidemiological studies

Rigorously assessing software reliability and safety

This paper summarises the state of the art in the assessment of software reliability and safety ("dependability"), and describes some promising developments. A sound demonstration of very high dependability is still impossible before operation of the software; but research is finding ways to make rigorous assessment increasingly feasible. While refined mathematical techniques cannot take the place of factual knowledge, they can allow the decision-maker to draw more accurate conclusions from the knowledge that is available