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Conventionally, the construction of a pair-matched sample selects treated and control units and pairs them in a single step with a view to balancing observed covariates x and reducing the heterogeneity or dispersion of treated-minus-control response differences, Y. In contrast, the method of cardinality matching developed here first selects the maximum number of units subject to covariate balance constraints and, with a balanced sample for x in hand, then separately pairs the units to minimize heterogeneity in Y. Reduced heterogeneity of pair differences in responses Y is known to reduce sensitivity to unmeasured biases, so one might hope that cardinality matching would succeed at both tasks, balancing x, stabilizing Y. We use cardinality matching in an observational study of the effectiveness of for-profit and not-for-profit private high schools in Chile—a controversial subject in Chile—focusing on students who were in government run primary schools in 2004 but then switched to private high schools. By pairing to minimize heterogeneity in a cardinality match that has balanced covariates, a meaningful reduction in sensitivity to unmeasured biases is obtained.

Effect modification means the magnitude or stability of a treatment effect varies as a function of an observed covariate. Generally, larger and more stable treatment effects are insensitive to larger biases from unmeasured covariates, so a causal conclusion may be considerably firmer if this pattern is noted if it occurs. We propose a new strategy, called the submax-method, that combines exploratory, and confirmatory efforts to determine whether there is stronger evidence of causality—that is, greater insensitivity to unmeasured confounding—in some subgroups of individuals. It uses the joint distribution of test statistics that split the data in various ways based on certain observed covariates. For L binary covariates, the method splits the population L times into two subpopulations, perhaps first men and women, perhaps then smokers and nonsmokers, computing a test statistic from each subpopulation, and appends the test statistic for the whole population, making 2L + 1 test statistics in total. Although L binary covariates define 2L interaction groups, only 2L + 1 tests are performed, and at least L + 1 of these tests use at least half of the data. The submax-method achieves the highest design sensitivity and the highest Bahadur efficiency of its component tests. Moreover, the form of the test is sufficiently tractable that its large sample power may be studied analytically. The simulation suggests that the submax method exhibits superior performance, in comparison with an approach using CART, when there is effect modification of moderate size. Using data from the NHANES I epidemiologic follow-up survey, an observational study of the effects of physical activity on survival is used to illustrate the method. The method is implemented in the R package submax which contains the NHANES example. An online Appendix provides simulation results and further analysis of the example.

This study investigated risk and protective factors associated with dyslexia and literacy development, both at the group and individual level, to gain more insight in underlying cognitive profiles and possibilities for compensation in high-IQ children. A sample of 73 Dutch primary school children included a dyslexic group, a gifted-dyslexic group, and a borderline-dyslexic group (i.e., gifted children with relative literacy problems). Children were assessed on literacy, phonology, language, and working memory. Competing hypotheses were formulated, comparing the core-deficit view to the twice-exceptionality view on compensation with giftedness-related strengths. The results showed no indication of compensation of dyslexia-related deficits by giftedness-related strengths in gifted children with dyslexia. The higher literacy levels of borderline children compared to gifted children with dyslexia seemed the result of both fewer combinations of risk factors and less severe phonological deficits in this group. There was no evidence for compensation by specific strengths more relevant to literacy development in the borderline group. Accordingly, the findings largely supported the core-deficit view, whereas no evidence for the twice-exceptionality view was found. Besides practical implications, the findings also add to knowledge about the different manifestations of dyslexia and associated underlying cognitive factors at the higher end of the intelligence spectrum.

From a sample of 1,242 third graders, prospective twice-exceptional students were selected using reading and math curriculum-based measures (CBMs), routinely used in Response to Intervention (RtI). These prospective twice-exceptional students were compared with non-twice-exceptional peers with similar strengths in either math or reading on CBMs and an end-of-year high-stakes achievement test. Students (both potentially twice-exceptional and not) who are potentially gifted in reading based on CBM performance did not differ significantly on the end-of-year outcomes in reading (p < .05); rather, students in both groups performed equally high. However, twice-exceptional students who are potentially gifted in math performed significantly lower on both end-of-year math and reading outcomes than non-twice-exceptional peers. Most of the end-of-year math subtest scores were negatively affected by the prospective twice-exceptional students’ deficits in reading, even though their math CBM scores placed them into a category representing giftedness in math. Implications for screening for twice-exceptionality are discussed.

A model for competing (resp. complementary) risks survival data where the failure time can be left (resp. right) censored is proposed. Product-limit estimators for the survival functions of the individual risks are derived. We deduce the strong convergence of our estimators on the whole real half-line without any additional assumptions and their asymptotic normality under conditions concerning only the observed distribution. When the observations are generated according to the double censoring model introduced by Turnbull, the product-limit estimators represent upper and lower bounds for Turnbull's estimator.

For enhancing the thermal fatigue resistance of bionic compacted graphite cast iron (CGI) laser-treated in water, the bionic units are treated twice with the laser to form an uneven bionic surface imitating the alternately soft and hard structure of a plant leaf, which can resist the tearing wind. The results show that this method, without changing the phase composition of the bionic unit, makes the austenite-to-martensite transformation more complete and the content of residual austenite is reduced, in addition, the microstructure coarsens and microhardness slightly turns lower. The twice laser process in water can effectively enhance the thermal fatigue resistance of bionic CGI by reducing the number of cracks in bionic units since the number of cross cracks on the bionic unit surface is the key factor, which affects their resistance to thermal crack propagation.

As clinical psychologists, our role is to provide psychological and educational testing, and counseling for children and their families. Our job is to understand the developmental trajectories and expectations across areas of functioning (i.e., behavior, self-regulation, cognitive, academic, and social), differentiate typical versus atypical development, and provide recommendations for accommodation, intervention, and growth in the home, at school, and in the community. As psychologists who work primarily with gifted and talented individuals, we see many with profound strengths as well as disabilities who are not easily categorized. These are twice-exceptional students. With twice-exceptionality, the diagnostic category, although important, is not the ultimate focus—identifying the needs and the strengths is equally, if not more, important.

Best practices in the identification of the twice-exceptional point to the use of multidimensional assessment that outlines specific areas of strength and concern. Students who are twice-exceptional remain a misunderstood population in schools, thus making identification that much more difficult. The purpose of this study was to review the extant literature in the field of twice-exceptional studies and to design a plan for identification to be used by school districts. This article reports on Project O2E, a state-funded collaboration program that resulted in a toolkit for identifying students who are twice-exceptional. Also included in this article is a discussion of issues raised during the implementation of the toolkit.