A Bootstrap Lasso + Partial Ridge Method to Construct Confidence Intervals for Parameters in High-dimensional Sparse Linear Models

Constructing confidence intervals for the coefficients of high-dimensional sparse linear models remains a challenge, mainly because of the complicated limiting distributions of the widely used estimators, such as the lasso. Several methods have been developed for constructing such intervals. Bootstrap lasso+ols is notable for its technical simplicity, good interpretability, and performance that is comparable with that of other more complicated methods. However, bootstrap lasso+ols depends on the beta-min assumption, a theoretic criterion that is often violated in practice. Thus, we introduce a new method, called bootstrap lasso+partial ridge, to relax this assumption. Lasso+partial ridge is a two-stage estimator. First, the lasso is used to select features. Then, the partial ridge is used to refit the coefficients. Simulation results show that bootstrap lasso+partial ridge outperforms bootstrap lasso+ols when there exist small, but nonzero coefficients, a common situation that violates the beta-min assumption. For such coefficients, the confidence intervals constructed using bootstrap lasso+partial ridge have, on average, $50\%$ larger coverage probabilities than those of bootstrap lasso+ols. Bootstrap lasso+partial ridge also has, on average, $35\%$ shorter confidence interval lengths than those of the de-sparsified lasso methods, regardless of whether the linear models are misspecified. Additionally, we provide theoretical guarantees for bootstrap lasso+partial ridge under appropriate conditions, and implement it in the R package "HDCI.

Minimum aberration designs for discrete choice experiments

A discrete choice experiment (DCE) is a survey method that givesinsight into individual preferences for particular attributes.Traditionally, methods for constructing DCEs focus on identifyingthe individual effect of each attribute (a main effect). However, aninteraction effect between two attributes (a two-factor interaction)better represents real-life trade-offs, and provides us a better understandingof subjects’ competing preferences. In practice it is oftenunknown which two-factor interactions are significant. To address theuncertainty, we propose the use of minimum aberration blockeddesigns to construct DCEs. Such designs maximize the number ofmodels with estimable two-factor interactions in a DCE with two-levelattributes. We further extend the minimum aberration criteria toDCEs with mixed-level attributes and develop some general theoreticalresults

In China's Wake: Has Asia Gained From China's Growth?

China’s growth has been rapid but the value of China's international trade has grown even faster. This trade-biased growth is bringing both challenges and opportunities for Asian economies that are highly integrated with Chinese trade networks. Moreover in ASEAN countries such as Indonesia and Malaysia, China’s success has been seen as a threat to its existing trade and manufacturing base. We use an historical simulation analysis to examine the impacts of China’s growth on Asian economies. We find that a decade of China’s growth has raised GDP per capita in the developed Asian economies by around 16%. The effect on the ASEAN-4 economies is not as strong but still large, the GDP of the ASEAN-4 economies increased by approximately 7%. The main source of these gains is found to be lower durable goods import costs which induce accumulation of machinery and equipment capital.Economic Growth, China, Trade Costs

The International Effects of China's Growth, Trade and Ecucation Booms

China’s international trade flows have increased by 500% since 1992, far outstripping GDP growth. Likewise tertiary education enrollments have increased by 300%. We simulate these changes using a multi-sector growth model of the Chinese and USA economies. A decade of trade biased growth in China is found to have a large effect on the USA economy – raising GDP approximately 3-4.5 percentage points. We also show that the trade bias in China’s growth accounts for more than half of the observed growth in tertiary enrolments in China. In contrast neutral growth has practically no effect on USA incomes or China’s stock of skilled labour. Finally the simulations reveal that China’s education boom per se has practically no long run impact on the USA economy. The results thus indicate that the pattern of productivity growth in exports sectors, as might be caused by falling trade costs, has been critical in transmitting benefits of Chinese growth to the world economy. They also point to an important link between falling trade costs and human capital formation.Economic Growth, China, Human Capital, Trade Costs

Documenting Macrophytes and Thier Habitat Preferences in Southeastern South Dakota

One of the most pressing environmental problems that waterbodies currently face is eutrophication. When eutrophication occurs in lakes, phytoplankton dominance increases and macrophyte (aquatic plant) populations decrease. Macrophyte population fluctuation can be used to detect eutrophication and indicate lake health. Despite this novel use of macrophytes, the state of South Dakota has few, if any, baseline public records of its macrophyte species. In an effort to establish a record and work towards the use of macrophytes as potential eutrophication indicators in South Dakota, this study seeks to provide a better understanding of the macrophytes that occur in the southeastern portion of the state and their relationships with lake habitats. The objectives of this study were to 1) survey the macrophytes of a small sample of lakes in southeastern South Dakota, 2) evaluate the relationships between existing macrophytes and the physical characteristics of their lakes, and 3) determine if there are any predictable habitat preferences. The survey was conducted at a total of 78 sample sites among two lakes during mid-summer 2020. Macrophyte samples were taken using a weighted sampling rake and substrates were visually estimated. Overall, ten different macrophytes types, including emergent, submerged, and free-floating species and genera, were recorded among sample sites. West 81 Lake had the highest species richness, with nine species present and a significantly higher (P \u3c 0.05) average species richness than Island Lake. Additionally, West 81 Lake showed a significantly higher (P \u3c 0.05) presence frequency of silt/muck substrates than Island Lake and a significant positive (P \u3c 0.05) relationship between percent silt/muck and species richness. Both lakes demonstrated a significant negative (P \u3c 0.05) relationship between percent clay and species richness. As the results suggest, both percent silt/muck and percent clay play important roles in determining the types of macrophytes in southeastern South Dakota lakes, and silt/muck dominated habitat systems appear to be preferred by a diverse array of macrophytes

Interparent agreement on the strengths and difficulties questionnaire : a Chinese study

This article reports on the first study to investigate interparent agreement when the Strengths and Difficulties Questionnaire (SDQ) is used to assess school-aged children. It is also the first study conducted in China on agreement between parents reporting on their child. Both parents of 380 girls and 320 boys completed the Strengths and Difficulties Questionnaire (Chinese version). Because reliabilities were poor, the Conduct Problems and Hyperactivity=Inattention subscales were merged to form an Externalizing Problems subscale, and the Peer Problems subscale as an independent variable was omitted from analyses. Consistent with past research, moderate to strong correlations were found between mother and father reports for emotional and behavioral problems, although interparent agreement was better for externalizing problems than internalizing problems for both girls and boys. Mothers reported significantly higher scores than fathers for prosocial behaviors for their sons. Findings suggest that, in general, one parent&rsquo;s report will be similar to the other&rsquo;s when the SDQ is used in the form adapted for this study. More work on the psychometric properties of the SDQ is needed in China.<br /

Preservation Methods Differ in Fecal Microbiome Stability, Affecting Suitability for Field Studies.

Immediate freezing at -20°C or below has been considered the gold standard for microbiome preservation, yet this approach is not feasible for many field studies, ranging from anthropology to wildlife conservation. Here we tested five methods for preserving human and dog fecal specimens for periods of up to 8 weeks, including such types of variation as freeze-thaw cycles and the high temperature fluctuations often encountered under field conditions. We found that three of the methods-95% ethanol, FTA cards, and the OMNIgene Gut kit-can preserve samples sufficiently well at ambient temperatures such that differences at 8 weeks are comparable to differences among technical replicates. However, even the worst methods, including those with no fixative, were able to reveal microbiome differences between species at 8 weeks and between individuals after a week, allowing meta-analyses of samples collected using various methods when the effect of interest is expected to be larger than interindividual variation (although use of a single method within a study is strongly recommended to reduce batch effects). Encouragingly for FTA cards, the differences caused by this method are systematic and can be detrended. As in other studies, we strongly caution against the use of 70% ethanol. The results, spanning 15 individuals and over 1,200 samples, provide our most comprehensive view to date of storage effects on stool and provide a paradigm for the future studies of other sample types that will be required to provide a global view of microbial diversity and its interaction among humans, animals, and the environment. IMPORTANCE Our study, spanning 15 individuals and over 1,200 samples, provides our most comprehensive view to date of storage and stabilization effects on stool. We tested five methods for preserving human and dog fecal specimens for periods of up to 8 weeks, including the types of variation often encountered under field conditions, such as freeze-thaw cycles and high temperature fluctuations. We show that several cost-effective methods provide excellent microbiome stability out to 8 weeks, opening up a range of field studies with humans and wildlife that would otherwise be cost-prohibitive