Design and analysis of computer experiments when the output is highly correlated over the input space

To build a predictor, the output of a deterministic computer model or “code” is often treated as a realization of a stochastic process indexed by the code's input variables. The authors consider an asymptotic form of the Gaussian correlation function for the stochastic process where the correlation tends to unity. They show that the limiting best linear unbiased predictor involves Lagrange interpolating polynomials; linear model terms are implicitly included. The authors then develop optimal designs based on minimizing the limiting integrated mean squared error of prediction. They show through several examples that these designs lead to good prediction accuracy.     

Chronic and Transient Poverty and Vulnerability to Poverty in the Philippines: Evidence Using a Simple Spells Approach

This paper uses panel data and two welfare indicators, namely per capita expenditure and per capita food expenditure, to determine the frequency that the households enter poverty and food poverty in the Philippines. Unlike other studies, this paper attributes similar factors to explain transient and chronic poverty but finds that these factors are more pronounced for the chronic case. Significant factors that contribute to both chronic and transient poverty and food poverty are the household heads’ low educational level, affiliation in economically unstable and risky occupations such as those in the agriculture, fishery and resource sectors and those who are unskilled laborers, the lack of health insurance and high dependency burden. The paper also finds that that vulnerability to poverty and food poverty in the Philippines is high especially in the rural districts and areas with armed conflict. Households that experience higher earnings, new job, abundant harvest, better health or receipt of remittance/inheritance are less likely to be chronically poor. Shocks related to labor market affect both transient and chronic food poverty while natural calamities or health deterioration of any household member increase the probability of the household falling into chronic food poverty. Policy suggestions to address both types of poverty are provided.     

Use of Slow Renditions to Facilitate Piano Proficiency in Young Musicians

For six weeks, four Suzuki piano students listened for a half hour daily to special recordings of repertoire being learned. Their piano teacher, blind to which pieces had been rendered at normal or at half speed, provided pre- and post-assessments of the performance on a battery of scales. Half-speed renditions resulted in modest facilitation which was discussed in terms of imagery, coding, and covert rehearsal.     

Advance Selling in the Presence of Speculators and Forward‐Looking Consumers

This article examines the pricing policy of a monopolist seller who may sell in advance of consumption in a market that comprises of myopic consumers, forward‐looking consumers, and speculators. The latter group has no consumption value for the goods and is in the market with the sole objective of making a profit by reselling the purchased goods shortly after. Consumers, although homogeneous in terms of their valuations, are different with respect to their perspectives. We show that in an “upward” market where the expected valuation increases over time, the optimal pricing policy is an ex ante “static” one where the seller “prices into the future” and prices the myopic consumers out of the advance market. However, in a “downward” market where the expected valuation decreases over time, the seller adopts a dynamic pricing strategy except for the case when higher initial sales can trigger more demand subsequently and when the downward trend is not too high. In this case, the seller prefers an ex ante “static” pricing strategy and deliberately prices lower initially to sell to speculators. We identify the conditions under which the seller benefits from the existence of speculators in the market. Moreover, although the presence of entry costs is ineffective as an entry deterrence, we determine the conditions under which exit costs can rein in speculative purchase.     

Academic mothers with disabilities: Navigating academia and parenthood during COVID-19

Academic mothers (including nonbinary, trans, and genderqueer parents) have always faced challenges in their profession due to systemic barriers and a “motherhood tax”; however, COVID-19 has exacerbated already existing inequalities (Oleschuk, 2020). This study examines how the pandemic has affected academic mothers with mental health and physical disabilities, as these voices often remain hidden and unheard in academia despite increased awareness of their presence (Brown & Leigh, 2018; Kelly & Senior, 2020). Here, we share the voices of 23 participants using a qualitative methodology drawing from social justice and feminist theories to highlight the lived experience of academic mothers with mental and/or physical disabilities and their experiences as a scholar and parent during COVID-19. Understanding the lived experience of this intersectional population can provide invaluable insights into ableist privilege within higher education, especially in the context of COVID-19 which has substantially disrupted work and homelife routines.     

A multi-faced buildup algorithm for three-dimensional packing problems

This paper provides a new approach to solving the three-dimensional packing problem. The heuristic developed uses a multi-faced buildup technique in the packing procedure for which there is no requirement for packed boxes to form flat layers. The basic algorithm is then augmented by a Look-ahead strategy. Experimental results indicate an average packing utilization of 87.8% which improve current benchmarks significantly. The new approaches given here add to heuristics currently available.     

The translation and development of a short form of the Korean language version of the multidimensional work ethic profile

The present research seeks to further facilitate a cross-cultural study on the work ethic construct by developing a short version of the Korean language version of the Multidimensional Work Ethic Profile (MWEP). Our research purpose is to provide researchers and practitioners with a short version of the Korean MWEP that can better meet their research needs by providing a thorough assessment of work ethic in a shorter time than the original full version. Results indicate that a shortened version demonstrates psychometric properties similar to the full version and is more practical and efficient to administer.     

Attribute Charts for Zero-Inflated Processes

The classical Shewhart c-chart and p-chart which are constructed based on the Poisson and binomial distributions are inappropriate in monitoring zero-inflated counts. They tend to underestimate the dispersion of zero-inflated counts and subsequently lead to higher false alarm rate in detecting out-of-control signals. Another drawback of these charts is that their 3-sigma control limits, evaluated based on the asymptotic normality assumption of the attribute counts, have a systematic negative bias in their coverage probability. We recommend that the zero-inflated models which account for the excess number of zeros should first be fitted to the zero-inflated Poisson and binomial counts. The Poisson parameter λ estimated from a zero-inflated Poisson model is then used to construct a one-sided c-chart with its upper control limit constructed based on the Jeffreys prior interval that provides good coverage probability for λ. Similarly, the binomial parameter p estimated from a zero-inflated binomial model is used to construct a one-sided np-chart with its upper control limit constructed based on the Jeffreys prior interval or Blyth–Still interval of the binomial proportion p. A simple two-of-two control rule is also recommended to improve further on the performance of these two proposed charts.     

A Regression Model for the AUC of Clustered Ordinal Test Results and Working Independent Optimal Weights

We study a regression model on the area under the receiver operating characteristic curves (AUC) for clustered (or repeatedly measured) test results. To account for cluster information, we consider a weighted estimating equation for Dodd and Pepe (2003 Dodd , L. , Pepe , M. ( 2003 ). Semiparametric regression for the area under the receiver operating charateristic curve . Journal of the American Statistical Association 98 : 409 – 417 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar])'s regression model with working independence weights. We find the optimal weight in the given class of working independence weights to minimize the variance (or MSE) of regression estimators. We apply the proposed procedure to analyzing our recent experiment on diagnosing a liver disorder. In this experiment, we investigated MRI images of patients having symptoms of potential liver disorder to compare the performance of different MRI picturing methods in testing for liver disorders.     

COMBINING HOUSEHOLD SURVEYS USING MASS IMPUTATION TO ESTIMATE POPULATION TOTALS

Pressure is often placed on statistical analysts to improve the accuracy of their population estimates. In response to this pressure, analysts have long exploited the potential to combine surveys in various ways. This paper develops a framework for combining surveys when data items from one of the surveys is mass imputed. The estimates from the surveys are combined using a composite estimator (CE). The CE accounts for the variability due to the imputation model and the surveys’ sampling schemes. Diagnostics for the validity of the imputation model are also discussed. We describe an application of combining the Australian Labour Force Survey and the National Aboriginal and Torres Strait Islander Health Survey to estimate employment characteristics about the Indigenous population. The findings suggest that combining these surveys is beneficial.