Evidence for data missing at random in youth physical activity monitoring research

This study examined whether or not activity monitor data collected as part of a typical 7-day physical activity (PA) measurement protocol can be expected to be missing at random. A total of 315 participants (9–18 years) each wore a SenseWear Armband monitor for 7 consecutive days. Participants were classified as “compliant” (86 boys and 124 girls) if they had recorded accelerometer data during 70% or more of the predefined awake time (7 AM–10 PM) on four different days; and “non-compliant” (44 boys and 51 girls) when not meeting these criteria. Linear mixed models were used to examine differences in energy expenditure (EE) levels by compliance across 10 different time periods. The results indicated that non-compliant girls were older (13.4 ± 2.9 vs. 12.2 ± 2.5) and taller (156.8 ± 10.3 vs. 152.8 ± 11.3) than their same gender compliant peers (P < .05). Comparisons of EE rates at segmented portions of the day revealed no differences between compliant and non-compliant groups (P ≥ .05). Differences in EE ranged from ?0.32 kcal · kg^?1 · h^?1 (before school time) to 0.62 kcal · kg^?1 · h^?1 (physical education class) in boys and ?0.39 kcal · kg^?1 · h^?1 (transportation from school) to 0.37 kcal · kg^?1 · hour^?1 (recess) in girls. The results showed that compliant and non-compliant individuals differed in a few demographic characteristics but exhibited similar activity patterns. This suggests that data were considered to be missing at random, but additional work is needed to confirm this observation in a representative sample of children using other types of activity monitors and protocols.     

The developmentalist and the study of biological risk: a view of the past with an eye toward the future

This paper has 2 goals: to review the history of the developmental study of infants and children at biological risk and to appraise the current state of the art. The scope of the review is from 1920 to the present and emphasizes the role of developmentalists. 4 research phases are identified, each reflecting aspects of the social, political, health, and psychological zeitgeist. First, from 1920 to World War II, research was primarily "catalog" and had diverse themes; however, several issues were raised that continue to have relevance. Second, during the postwar years, research often focused on the cognitive and emotional residuals of handicaps, particularly cerebral palsy and poliomyelitis. Third, the 1960s marked the funding of major seminal longitudinal investigations of perinatal risk factors, and studies of very young infants "at risk." And fourth, in the last and current period, technological advances of the 1970s first applied to research with normally developing children were then extended to at-risk groups and revolutionized the methods of studying risk. Finally, we suggest that, although a considerable amount of information has been obtained about developmental phenomena subsequent to biological risk, our research literature is fragmented and difficult to synthesize. We conclude by offering strategies to foster research and the integration of knowledge.     

Instructional design for advanced learners: Establishing connections between the theoretical frameworks of cognitive load and deliberate practice

Cognitive load theory (CLT) has been successful in identifying instructional formats that are more effective and efficient than conventional problem solving in the initial, novice phase of skill acquisition. However, recent findings regarding the “expertise reversal effect” have begun to stimulate cognitive load theorists to broaden their horizon to the question of how instructional design should be altered as a learner's knowledge increases. To answer this question, it is important to understand how expertise is acquired and what fosters its development. Expert performance research, and, in particular, the theoretical framework of deliberate practice have given us a better understanding of the principles and activities that are essential in order to excel in a domain. This article explores how these activities and principles can be used to design instructional formats based on CLT for higher levels of skills mastery. The value of these formats for e-learning environments in which learning tasks can be adaptively selected on the basis of online assessments of the learner's level of expertise is discussed. In their preparation of this article, the first and last authors were supported by an Internationalization grant from the Netherlands Organization for Scientific Research (NWO, The Hague, project number 411-01-010).     

A further analysis of the ethics of representation in virtual reality: Multi-user environments

This is a follow-up article toPhilip Brey's ``The ethics of representation andaction in Virtual Reality' (published in thisjournal in January 1999). Brey's call for moreanalysis of ethical issues of virtual reality(VR) is continued by further analyzing issuesin a specialized domain of VR – namelymulti-user environments. Several elements ofBrey's article are critiqued in order to givemore context and a framework for discussion.Issues surrounding representations ofcharacters in multi-user virtual realities aresurveyed in order to focus attention on theimportance of additional discussion andanalysis of specialized aspects of VR.     

Effects of student-facilitated learning on instructional facilitators

We investigated perceptions about learning strategy use and instructional roles among a sample of high needs adolescents (n = 230) who acted as near-peer instructional facilitators. The sample was drawn from science and mathematics classes in nonselective public secondary schools in New York City. Students participated in an inschool intervention that draws on social constructivism, theory and research on metacognition and learning strategies, role theory, and empirical findings from the peer-to-peer learning literature to promote advanced achievement among students who act as facilitators. Using a pre- and post-test single group design, we surveyed student instructional facilitators before and after program participation and related their perceptions about learning strategy use and perceptions about teaching roles to data about academic achievement. We found no survey gains in student perceptions about learning strategies or instructional roles between pre-survey (fall) and post-survey (spring). We found small but significant effects of individual perceptions about learning strategies and teaching roles on academic gains among instructional facilitators. The study also suggests that an in-school near-peer facilitated learning program can be an effective means to raise achievement in urban high schools. The study provides partial support for theories that hold that metacognition and role perceptions are involved in the academic gains of instructional facilitators, as gains in these dimensions were small compared to achievement gains.