On the asymptotic efficiency of the multisample location-scale rank tests and their adjustment for ties

summary:Explicit formulas for the non-centrality parameters of the limiting chi-square distribution of proposed multisample rank based test statistics, aimed at testing the hypothesis of the simultaneous equality of location and scale parameters of underlying populations, are obtained by means of a general assertion concerning the location-scale test statistics. The finite sample behaviour of the proposed tests is discussed and illustrated by simulation estimates of the rejection probabilities. A modification for ties of a class of multisample location and scale test statistics, based on ranks and including the proposed test statistics, is presented. It is shown that under the validity of the null hypothesis these modified test statistics are asymptotically chi-square distributed provided that the score generating functions fulfill the imposed regularity conditions. An essential assumption is that the matrix, appearing in these conditions, is regular. Conditions sufficient for the validity of this assumption are also included

Children born prematurely: Cognitive outcomes and preliminary findings for subsequent intervention

Well-established evidence shows that children born preterm/low birth weight (LBW) are at increased risk of academic difficulties (Lee, Yeatman, Luna, & Feldman, 2011; Pritchard et al., 2009) and, despite global IQ scores within the normal range, nonetheless display lower academic performance than their same age peers (Bhutta, Cleves, Casey, Cradock, & Anand, 2002; Kerr-Wilson, Mackay, Smith, & Pell, 2011). This is not fully understood and previous attempts to improve these circumstances through means of cognitive intervention have met with little success. Therefore, the current thesis investigates possible underlying mechanisms of this intellectual disparity and tests the effectiveness of one potential intervention. In doing so, the studies presented focus specifically on fluid intelligence (Taub, 2002). The investigation through fluid intelligence is relatively novel in the current literature and therefore worthy of further exploration. Normal individual differences in fluid intelligence have been explained with reference to information processing parameters. Previous studies have shown that children born preterm/LBW have impairments in basic processes identified with executive function (Aarnoudse-Moens, Smidts, Oosterlaan, Duivenvoorden, & Weisglas-Kuperus, 2009; Mulder, Pitchford, Hagger, & Marlow, 2009). However, the current study is the first to test whether differences in fluid intelligence, as measured by the Cattell Culture Fair Tests, between preterm (n = 217) and typically developing children (n = 145) could be accounted for by differences in working memory and cognitive flexibility, as measured by the digit span tasks and the Wisconsin Card Sorting Test respectively. Results indicate that the seven to nine years old preterm cohort performed less well on measures of fluid intelligence than their peers across all age groups and their differences were partially mediated by both working memory and cognitive flexibility in a multiple mediation analysis. It also identified at least one year of developmental delay in fluid intelligence between the clinical group and their peers. Provided with evidence from Study 1 and parallel research suggesting that computerized working memory training may enhance working memory and fluid intelligence in non-clinical groups (Jaeggi, Buschkuehl, Jonides, & Perrig, 2008; Klingberg, Forssberg, & Westerberg, 2002; Studer et al., 2009), the second goal of this thesis was to conduct a preliminary study to investigate the feasibility of cognitive training for children born preterm/LBW. Therefore, in the second study, the utility of a brief adaptive working memory span training program (Buschkuehl, Jaeggi, Kobel, & Perrig, 2008) was tested in typically developing children. Sixty-three children, aged seven to nine years, were randomly assigned to one of three groups: Intervention, active control and passive control. The intervention group was trained in the adaptive version of the working memory span task and the active control group was trained in the nonadaptive version. Both groups trained for 15 minutes each day for a duration of 20 days. Participants in the passive control group participated only in pre and post assessments. All participants were assessed using the digit span and spatial span tasks for measuring working memory, the Stroop task for measuring executive control, a reaction time task for measuring processing speed and the Raven’s Standard Progressive Matrices for measuring fluid intelligence. Results indicate that children in the intervention group improved on their trained task and demonstrated significant far transfer effects on the assessment of fluid intelligence compared to both control groups. However, no near transfer to other measures was found. The reason behind the occurrence of far transfer effect without evidence of near transfer effects was unclear. However, given that the adaptive complex working memory training task was not in any way similar to the fluid intelligence measure, significant differences in fluid intelligence gains were unlikely to have been a consequence of practice or general familiarity effects but, rather, a consequence of the training. Although Study 1 identified that working memory and cognitive flexibility partially mediate birth status-related differences in Gf, the impact of these variables on academic performance in children born preterm is still unknown. Nonetheless, current evidence of far transfer to fluid intelligence after adaptive complex working memory span training provides support for the utility of WM training and modifiability in Gf. This in turn provides a preliminary evidence-base approach for psychologists to work toward providing neuro-remediation treatment options to targeted clinical groups, such as those born preterm with fluid intelligence deficiencies. In combination, the outcomes of these two studies provide both a theoretical contribution to our understanding of the deficits observed in children born preterm and an applied contribution to beginning the process of developing appropriate intervention programmes suitable for this clinical group in the future, with hopeful prospects for improving cognitive outcomes

Management of Degenerative Cervical Myelopathy and Spinal Cord Injury

The present Special Issue is dedicated to presenting current research topics in DCM and SCI in an attempt to bridge gaps in knowledge for both of the two main forms of SCI. The issue consists of fourteen studies, of which the majority were on DCM, the more common pathology, while three studies focused on tSCI. This issue includes two narrative reviews, three systematic reviews and nine original research papers. Areas of research covered include image studies, predictive modeling, prognostic factors, and multiple systemic or narrative reviews on various aspects of these conditions. These articles include the contributions of a diverse group of researchers with various approaches to studying SCI coming from multiple countries, including Canada, Czech Republic, Germany, Poland, Switzerland, United Kingdom, and the United States

Phylogenomic, Biogeographic, and Evolutionary Research Trends in Arachnology

This book focuses on systematics, biogeography, and evolution of arachnids, a group of ancient chelicerate lineages that have taken on terrestrial lifestyles. The book opens with the questions of what arachnology represents, and where the field should go in the future. Twelve original contributions then dissect the current state-of-the-art in arachnological research. These papers provide innovative phylogenomic, evolutionary and biogeographic analyses and interpretations of new data and/or synthesize our knowledge to offer new directions for the future of arachnology