A Multidimensional Finite Mixture Structural Equation Model for Nonignorable Missing Responses to Test Items

We propose a structural equation model, which reduces to a multidimensional latent class item response theory model, for the analysis of binary item responses with nonignorable missingness. The missingness mechanism is driven by 2 sets of latent variables: one describing the propensity to respond and the other referred to the abilities measured by the test items. These latent variables are assumed to have a discrete distribution, so as to reduce the number of parametric assumptions regarding the latent structure of the model. Individual covariates can also be included through a multinomial logistic parameterization for the distribution of the latent variables. Given the discrete nature of this distribution, the proposed model is efficiently estimated by the expectation–maximization algorithm. A simulation study is performed to evaluate the finite-sample properties of the parameter estimates. Moreover, an application is illustrated with data coming from a student entry test for the admission to some university courses.     

Grammar and text: an experiment in teacher training / Gramática y texto: un experimento en la formación de profesores

Abstract

The article describes an experiment in teaching training undertaken in the context of the Masters programme in Teacher Training (for primary school teachers) at the Lisbon College of Education. The training experiment was able to: (1) incorporate mother tongue teaching into the broader curriculum; (2) relate the teaching of texts and the teaching of grammar; and (3) integrate the theoretical and practical dimensions of teacher training. The didactic scheme adopted relies on theoretical assumptions such as the concept of the integrated curriculum, the model of didactic sequence and the principles of socio-discursive interactionism. This training experiment has proved to be particularly useful for all the participants in the process (teachers of the course; trainee teachers; children in the schools; and the form teachers of the classes where the trainees do their practice). As a result of it, there has been a clear improvement in the quality of the teaching provided by our trainees in the domains of writing and grammar. The main advantages of this approach are that: (1) it structures the teaching of writing and grammar; (2) it uses projects to socially contextualize writing tasks; (3) it develops various language skills in an integrated fashion, while at the same time working on different areas of knowledge; and (4) it defines forms of spiral progression.     

Traffic modeling for communications networks: A multifractal approach based on few parameters

In this work, in order to model network traffic processes, an efficient multifractal model is proposed based on fewer parameters than other models present in the literature, called 2PEMV. The 2PEMV model (2-Parameter Exponential Modeling for Multipliers’ Variance) is based on a multiplicative cascade in the wavelet domain capable of synthesizing communication network traffic traces which present characteristics such as self-similarity and wide Multifractal Spectrum Width (MSW). For such a purpose, in the 2PEMV model, the energy decay of the wavelet coefficients is captured by means of an exponential modeling for the multipliers’ variance along the cascade scales. The performance of the 2PEMV model to represent the network traffic characteristics is evaluated in comparison to other models present in the literature through simulations that are carried out using real communication network traffic traces.     

Total Protein of Whole Saliva as a Biomarker of Anaerobic Threshold

Saliva provides a convenient and noninvasive matrix for assessing specific physiological parameters, including some biomarkers of exercise. We investigated whether the total protein concentration of whole saliva (TPWS) would reflect the anaerobic threshold during an incremental exercise test. After a warm-up period, 13 nonsmoking men performed a maximum incremental exercise on a cycle ergometer. Blood and stimulated saliva were collected during the test. The TPWS anaerobic threshold (PAT) was determined using the Dmax method. The PAT was correlated with the blood lactate anaerobic threshold (AT; r = .93, p < .05). No significant difference (p = .16) was observed between PAT and AT. Thus, TPWS provides a convenient and noninvasive matrix for determining the anaerobic threshold during incremental exercise tests.     

Short-term tracking of performance and health-related physical fitness in girls: The Healthy Growth in Cariri Study

Abstract

The main purpose of this study was to track the performance and health-related physical fitness of girls from Brazil's Cariri region. In the “Healthy Growth in Cariri Study”, 294 girls from public and private schools were divided into four age cohorts – 8, 10, 12, and 14 years – and followed for three consecutive years, with an assessment every 6 months. Shuttle run, hand grip, standing long jump, trunk lift, curl-up, 12-min run, and fatness were used to rate physical fitness performance and health-related components on each of six occasions. Tracking was done in a stepwise manner, using auto-correlation, by modelling the individual history of change in performance of each girl, and using Foulkes and Davies’ γ-coefficient. SPSS 18.0 and TIMEPATH were used for data analysis. Auto-correlations evidenced low-to-moderate values in almost all components of performance and health-related physical fitness. Intra-individual tracking analysis showed large variation in all fitness components as a result of a wide spread in individual history of change in fitness performance. Population estimates of γ were low in all tests. Our results show low-to-moderate tracking of physical fitness components of girls. A wide range of intra-individual and inter-variability in fitness development was observed.     

Creatine Kinase Activity Weakly Correlates to Volume Completed Following Upper Body Resistance Exercise

In the current study, we examined the relationship between serum creatine kinase (CK) activity following upper body resistance exercise with a 1- or 3-min rest between sets. Twenty men performed two sessions, each consisting of four sets with a 10-repetition maximum load. The results demonstrated significantly greater volume for the 3-min condition (M = 4,156 kg, SD = 867, for 3 min; vs. M = 3,503 kg, SD = 759, for 1 min; p < .001), with no significant differences in delta CK activity between conditions (p = .574). Nevertheless, there was a weak correlation between the delta CK activity and total volume of exercise completed (r = .55 with a 1-min rest, and r =.45 with a 3-min rest). Therefore, the volume following upper body resistance exercise correlates weakly with serum CK levels, irrespective of rest interval length between sets.     

Physical fitness percentiles for Portuguese children and adolescents aged 10–18 years

Abstract

This study aimed to produce age- and sex-specific physical fitness reference data for Portuguese youth; to report the prevalence of youth in the healthy zone of physical fitness according to the FITNESSGRAM^® criteria; to verify the agreement between the Portuguese physical fitness percentiles and the FITNESSGRAM^® healthy zones. In 2008, 22,048 Portuguese children and adolescents (10–18 years) were evaluated. Physical fitness (curl-ups, push-ups, 20-m shuttle run and modified-back-saver-sit-and-reach tests) was evaluated using the FITNESSGRAM^® Test Battery 8.0. Smoothed percentile curves were estimated using Cole’s LMS method. Boys consistently outperformed girls in every physical fitness test, except for the modified-back-saver-sit-and-reach tests. In both sexes and for all physical fitness tests, higher percentile values were observed at older ages. The 50th percentile of all physical fitness tests had the highest accuracy to discriminate between under healthy zone and healthy zone of the FITNESSGRAM^®. Portuguese schools and physical education teachers may considerer the 50th percentile for age and sex or the FITNESSGRAM^® criteria for classifying participants in the healthy zone as acceptable cut-offs, above which youth should be considered fit. These reference values can be used as normative data and for baseline values for subsequent surveillance of the physical fitness of Portuguese youth.     

Contributions from citizen science to science education: an examination of a biodiversity citizen science project with schools in Central Europe

ABSTRACT

Despite the rising popularity of Citizen Science (CS) projects, there is little empirical evidence for effects on learning outcomes, particularly when young people are involved. It is also often not clear how CS projects are linked to science education (SE) research. The aim of this study was to examine biodiversity CS projects in an outdoor school class context and to measure the effects on individual learning outcomes (ILOs) with a perspective for SE. Five learning outcomes considered important for CS were tested: interest, self-efficacy/mastery, motivation, behaviour and attitude. These ILOs were measured via eight different scales and tested in an evaluation study of a large CS project with 428 students aged 8–18. Students recorded hedgehogs, wild bee activity, birds and butterflies in gardens. Results showed that students’ interest and motivation, as well as perceived mastery increased during the project. Most remarkably, positive attitudes towards wild animals, natural gardens and biodiversity rose significantly. For most ILOs there were significant differences between age groups: Primary school students showed the highest ILOs and also provided most database entries. The authors describe how well biodiversity CS projects contribute to SE aims and how discrepancies between educational and scientific aims in CS projects may be addressed.     

Knowledge,its Application,and Attitudes Associated with the Reading of Diverse Genres of Science Texts

The purpose of this article is to assess the knowledge, application of knowledge, and attitudes associated with the reading of different genres of expository science texts. We assigned approximately half of a sample consisting of 220 students 14–15 years of age, chosen at random, to read an excerpt from a popular scientific text, and the other half to read an excerpt from a textbook addressing the same topic. Readers took knowledge and application tests immediately after the reading and again 15 days later. Students also took knowledge and reading proficiency pre-tests, and attitude tests related to the selected texts. Overall, girls scored higher than boys and readers of the popular scientific text scored higher than their colleagues who read the textbook excerpt. We noted interaction between ‘reader gender’ and ‘genre of the text read’ in terms of long-term learning based on the reading. Attitude regarding the text read appears as an important factor in explaining behavior of boys who read the popular scientific text. Surprisingly, knowledge and application test scores were not statistically different among girls with different degrees of reading proficiency who read the textbook excerpt. In addition, on the application tests, among the boys who read the popular scientific text, good readers scored lower than their colleagues who read the textbook excerpt. In our opinion, this study can serve to show that ‘reading in science education’ is not a trivial matter and we feel that the subject merits more in-depth investigation.     

Navigating the complexity of qualitative research in postmodern contexts: assemblage,critical reflexivity,and communion as guides

For graduate students and other emerging qualitative researchers, the ever-evolving and sometimes conflicting perspectives, methodologies, and practices within various post-positivist frameworks (e.g. feminist, critical, Indigenous, participatory) can be overwhelming. Qualitative researchers working within postmodern contexts of multiplicity and ambiguity are tasked with working through challenges – related to methods, interpretation, and representation – throughout the research process. Through examining related literature and incorporating my own experiences, I explore ethical dilemmas that social justice-oriented qualitative researchers may encounter as a result of conflicting multiplicities of difference among researcher(s), participants, and readers. Such dilemmas include incongruent interpretations between participants and researchers, and participants’ and researchers’ conflicting desires about what should be shared, intercultural (mis)interpretations, rapport issues, and conflicts between research life and home life. I consider how combining the practices of attending to assemblages, engaging in critical reflexivity, and centralizing communion may be useful in navigating relationships and ethical dilemmas in qualitative research.