Using compositional data analysis to explore accumulation of sedentary behavior,physical activity and youth health

Purpose:The study aimed to describe youth time-use compositions,focusing on time spent in shorter and longer bouts of sedentary behavior and physical activity(PA),and to examine associations of these time-use compositions with cardiometabolic biomarkers.Methods:Accelerometer and cardiometabolic biomarker data from 2 Australian studies involving youths 7-13 years old were pooled(complete cases with accelerometry and adiposity marker data,n=782).A 9-component time-use composition was formed using compositional data analysis:time in shorter and longer bouts of sedentary behavior;time in shorter and longer bouts of light-,moderate-,or vigorous-intensity PA;and"other time"(i.e.,non-wear/sleep).Shorter and longer bouts of sedentary time were defined as<5 min and>5 min,respectively.Shorter bouts of light-,moderate-,and vigorous-intensity PA were defined as<1 min;longer bouts were defined as≥1 min.Regression models examined associations between overall time-use composition and cardiometabolic biomarkers.Then,associations were derived between ratios of longer activity patterns relative to shorter activity patterns,and of each intensity level relative to the other intensity levels and"other time",and cardiometabolic biomarkers.Results:Confounder-adjusted models showed that the overall time-use composition was associated with adiposity,blood pressure,lipids,and the summary score.Specifically,more time in longer bouts of light-intensity PA relative to shorter bouts of light-intensity PA was significantly associated with greater body mass index z-score(zBMI)(β=1.79;SE=0.68)and waist circumference(β=18.35,SE=4.78).When each activity intensity was considered relative to all higher intensities and"other time",more time in light-and vigorous-intensity PA,and less time in sedentary behavior and moderate-intensity PA,were associated with lower waist circumference.Conclusion:Accumulating PA,particularly light-intensity PA,in frequent short bursts may be more beneficial for limiting adiposity compared to accumulating the same amount of PA at these intensities in longer bouts.     

The influence of social interaction on meaning construction in a virtual community

As proposed by social constructive theorists, meaningful learning and individual development were achieved through social interaction. To foster social interaction among students, this study formed an online learning community in which they played multiple roles as writers, editors and commentators. In playing different roles, they read peers' texts, edited peers' errors, evaluated peer editors' corrections and finally reconstructed their own texts. Results of this study showed that the multiple roles they played allowed them to have opportunities to view their own texts from others' perspectives. Based on these perspectives, they were more willing to acquire information from and contribute information to peers. All of this extensive information acquisition and contribution resulted in meaning construction of texts as active students improved their final drafts in both local revision (grammatical correction) and global revision (the style, organisation and development of a text) after receiving and evaluating feedback from peer editors. Their final drafts were very different from those of passive students whose first and final drafts were almost the same despite some grammatical revisions. This study suggests that, rather than relying only on an examination of students' final drafts, there may be benefits in teachers encouraging students to actively participate in social interaction by reading peers' texts, editing peers' errors and evaluating peer editors' corrections during text revisions.     

The impact of individual differences on e‐learning system satisfaction: A contingency approach

This study investigated the impact of contingent variables on the relationship between four predictors and students' satisfaction with e‐learning. Five hundred and twenty‐two university students from 10 intact classes engaging in online instruction were asked to answer questionnaires about their learning styles, perceptions of the quality of the proposed predictors and satisfaction with e‐learning systems. The results of analysis of variance and structural equation modelling analyses showed that two contingent variables, gender and job status, significantly influenced the perceptions of predictors and students' satisfaction with the e‐learning system. This study also found a statistically significant moderating effect of two contingent variables, student job status and learning styles, on the relationship between predictors and e‐learning system satisfaction. The results suggest that a serious consideration of contingent variables is crucial for improving e‐learning system satisfaction. The implications of these results for the management of e‐learning systems are discussed.     

Stability and correlates of student evaluations of teaching at a Chinese university

This paper examines the stability and validity of a student evaluations of teaching (SET) instrument used by the administration at a university in the PR China. The SET scores for two semesters of courses taught by 435 teachers were collected. Total 388 teachers (170 males and 218 females) were also invited to fill out the 60‐item NEO Five‐Factor Inventory together with a demographic information questionnaire. The SET responses were found to have very high internal consistency and confirmatory factor analysis supported a one‐factor solution. The SET re‐test correlations were .62 for both the teachers who taught the same course (n = 234) and those who taught a different course in the second semester (n = 201). Linguistics teachers received higher SET scores than either social science or humanities or science and technology teachers. Student ratings were significantly related to Neuroticism and Extraversion. Regression results showed that the Big‐Five personality traits as a group explained only 2.6% of the total variance of student ratings and academic discipline explained 12.7% of the total variance of student ratings. Overall the stability and validity of SET was supported and future uses of SET scores in the PR China are discussed.     

Persistence in the determination of work-related training participation: Evidence from the BHPS, 1991–1997

In this paper we investigate the role of workers’ training history in determining current training-incidence. The analysis is conducted on an unbalanced sample comprising information on approximately 5000 employees from the first seven waves of the BHPS. Training participation is modelled as a dynamic random effects probit model where the effects of unobserved heterogeneity and initial conditions are accounted for in a fashion consistent with methods proposed by Chamberlain (1984) and Wooldridge (2005), respectively. The results suggest that prior training experience is a significant determinant of a worker's participation in a current training episode comparable with other formal educational qualifications.     

Connecting high school physics experiences,outcome expectations,physics identity,and physics career choice: A gender study

This study explores how students' physics identities are shaped by their experiences in high school physics classes and by their career outcome expectations. The theoretical framework focuses on physics identity and includes the dimensions of student performance, competence, recognition by others, and interest. Drawing data from the Persistence Research in Science and Engineering (PRiSE) project, which surveyed college English students nationally about their backgrounds, high school science experiences, and science attitudes, the study uses multiple regression to examine the responses of 3,829 students from 34 randomly selected US colleges/universities. Confirming the salience of the identity dimension for young persons' occupational plans, the measure for students' physics identity used in this study was found to strongly predict their intended choice of a physics career. Physics identity, in turn, was found to correlate positively with a desire for an intrinsically fulfilling career and negatively with a desire for personal/family time and opportunities to work with others. Physics identity was also positively predicted by several high school physics characteristics/experiences such as a focus on conceptual understanding, real‐world/contextual connections, students answering questions or making comments, students teaching classmates, and having an encouraging teacher. Even though equally beneficial for both genders, females reported experiencing a conceptual focus and real‐world/contextual connections less frequently. The explicit discussion of under‐representation of women in science was positively related to physics identity for female students but had no impact for male students. Surprisingly, several experiences that were hypothesized to be important for females' physics identity were found to be non‐significant including having female scientist guest speakers, discussion of women scientists' work, and the frequency of group work. This study exemplifies a useful theoretical framework based on identity, which can be employed to further examine persistence in science, and illustrates possible avenues for change in high school physics teaching. © 2010 Wiley Periodicals, Inc. J Res Sci Teach 47: 978–1003, 2010     

Bridging scientific reasoning and conceptual change through adaptive web‐based learning

This study reports an adaptive digital learning project, Scientific Concept Construction and Reconstruction (SCCR), and examines its effects on 108 8th grade students' scientific reasoning and conceptual change through mixed methods. A one‐group pre‐, post‐, and retention quasi‐experimental design was used in the study. All students received tests for Atomic Achievement, Scientific Reasoning, and Atomic Dependent Reasoning before, 1 week after, and 8 weeks after learning. A total of 18 students, six from each class, were each interviewed for 1 hour before, immediately after, and 2 months after learning. A flow map was used to provide a sequential representation of the flow of students' scientific narrative elicited from the interviews, and to further analyze the level of scientific reasoning and conceptual change. Results show students' concepts of atoms, scientific reasoning, and conceptual change made progress, which is consistent with the interviewing results regarding the level of scientific reasoning and quantity of conceptual change. This study demonstrated that students' conceptual change and scientific reasoning could be improved through the SCCR learning project. Moreover, regression results indicated students' scientific reasoning contributed more to their conceptual change than to the concepts students held immediately after learning. It implies that scientific reasoning was pivotal for conceptual change and prompted students to make associations among new mental sets and existing hierarchical structure‐based memory. © 2009 Wiley Periodicals, Inc. J Res Sci Teach 47: 91–119, 2010     

Four case studies,six years later: Developing system thinking skills in junior high school and sustaining them over time

This study examines the process by which system thinking perceptions develop within the context of a water cycle curriculum. Four junior high school students undergoing an especially designed inquiry‐based intervention were closely observed before, during, immediately after, and 6 years after completing a year long systems‐based learning program. The employed research tools included observations, semi‐structured interviews, and a number of “concept viewing” tools (drawings, concept maps, and repertory grids). Out of the data, four distinct “stories,” each presenting a different way of constructing hydro system mental models, are described. The paper's main conclusion is that students develop their systems mental models and remember the learned material based on learning patterns that tend to remain unchanged over time. Consequently, in order to facilitate efficient and lasting construction of students' system models, learning experiences should harness these, and especially the meta‐cognitive learning pattern, which holds special significance for constructing systems. © 2010 Wiley Periodicals, Inc. J Res Sci Teach 47: 1253–1280, 2010