Analysing expertise through data mining: an example based on treading water

Abstract

A classification system of treading water based on a conceptual typology was first established and then verified empirically. The typology was established on two concepts: the nature of the forces created within the water and the type of inter-limb coordination used. Thirty-eight participants were videotaped while treading water. Multivariate statistics were used to understand how the different behavioural types related to expertise. Three distinct groups of coordination patterns were adopted during treading water. A support vector machine procedure was used as a confirmatory procedure. The data mining process provides a methodological framework to analyse expertise in sports activities, and in this context suggests that a taxonomy can be established among the numerous coordination solutions that allow humans to create stabilising forces in the water.     

Sleep restriction and degraded reaction-time performance in Figaro solo sailing races

Abstract

In solo offshore sailing races like those of the Solitaire du Figaro, sleep must be obtained in multiple short bouts to maintain competitive performance and safety. Little is known about the amount of sleep restriction experienced at sea and the effects that fatigue from sleep loss have on sailors’ performance. Therefore, we assessed sleep in sailors of yachts in the Figaro 2 Beneteau class during races and compared response times on a serial simple reaction-time test before and after races. Twelve men (professional sailors) recorded their sleep and measured their response times during one of the three single-handed races of 150, 300 and 350 nautical miles (nominally 24–50 h in duration). Total estimated sleep duration at sea indicated considerable sleep insufficiency. Response times were slower after races than before. The results suggest that professional sailors incur severe sleep loss and demonstrate marked performance impairment when competing in one- to two-day solo sailing races. Competitive performance could be improved by actively managing sleep during solo offshore sailing races.     

Situational Indexes of Achievement Motivation,Help-Seeking,and Performance: Influences of the Learning Context and Gender Differences

Abstract

Sixteen college athletes and non-athletes were given 10 30-sec. practice trials to learn how to balance on a stabilometer. The next day they were allowed three more trials alone and three trials before a group of spectators. The non-athletes were significantly better on two of the three trials performed in front of the spectators. They also performed better than the athletes throughout the ten practice trials, although the tenth and last trial approached but did not yield a significant difference at the .05 level.     

Development and use of a test instrument to measure biology teachers’ content knowledge (CK) and pedagogical content knowledge (PCK)

Research on teachers’ professionalism and professional development has increased in the last two decades. A main focus of this line of research has been the cognitive component of teacher professionalism, i.e., professional knowledge. Most of the previous studies on teacher knowledge—such as the Learning Mathematics for Teaching (LMT) (Hill et al. 2004), the Professional Competence of Teachers, Cognitively Activating Instruction, and Development of Students´ Mathematical Literacy (COACTIV) (Baumert et al. 2010), and the Mathematics Teaching in the 21st Century (MT21) (Schmidt et al. 2007) studies—have been conducted in the field of mathematics teachers’ pedagogical content knowledge (PCK) and content knowledge (CK). There have been few comparable studies conducted with science teachers, especially biology teachers. To fill the gap, this study examines the development and use of instruments to measure biology teachers’ CK and PCK. In particular, this study describes a method to develop reliable, objective, and valid instruments measuring teachers’ CK and PCK in four steps by the use of empirical data of students. Additionally, the study explores whether CK and PCK might be measured as separate knowledge categories by using a paper-and-pencil test. This paper presents a theoretical model that guides test development and provides steps to develop and validate the instruments. Details are also provided regarding the computation of the Rasch scale score measures for 158 biology teachers. The results indicate that the instruments measured teachers’ CK and PCK in an objective, valid, and reliable way. This suggests that the new instruments can be used in combination with classroom observations to examine teaching quality and further its relation to student learning.     

Why are teacher recommendations at the transition from primary to secondary education socially biased? A mixed-methods research

The consequences of educational differentiation have been at the centre of research in sociology of education during the past decades. Processes of educational allocation have, however, received much less attention. Despite the fact that research has shown that teacher recommendations in France and Germany are partly determined by pupils’ social background, studies that inquire into the causes of this social bias seem to be virtually inexistent. This study aims to examine whether teacher recommendations at the transition from primary to secondary education in Flanders (northern, Dutch-speaking part of Belgium) are also socially biased, and if so what causes these differentials in advice, using a mixed-methods design. We found the advice given by primary school teachers to be partly determined by pupils’ social background. Analysis of the qualitative data suggests that teachers tend to evaluate pupils from low socio-economic status backgrounds less positively, due to their emphasis on specific pupil characteristics.     

Multilevel Mediation: Cumulative Contextual Risk,Maternal Differential Treatment,and Children's Behavior Within Families

This study tests the hypothesis that links between contextual risk and children's outcomes are partially explained by differential parenting. Using multi‐informant measurement and including up to four children per family (M_age = 3.51, SD = 2.38) in a sample of 397 families, indirect effects (through maternal differential parenting: self‐reported and observed) of cumulative contextual risk on four child outcomes were investigated. Cumulative risk was associated with higher levels of differential parenting and, in turn, with higher levels of behavioral problems. Indirect effects were strongest for attentional and social problems but also evident for aggression. The link between differential parenting and outcome was moderated by favoritism, but this was only evident for maternal report and strongest for aggression.     

Hydrodynamics and oxygen transfer in a novel extra-loop fluidized bed bioreactor

In this paper, the characteristics of fluid mixing time in a novel extra-loop fluidized bed were studied. The results showed that the mixing time was shortened with the increase of fluid velocity. All the discrete numbers of the reactor were above 0.2. The serial number n was 2.5 -3.0. It was judged accordingly that the reactor fluid state was continous stirred tank reactor （CSTR） mainly. When the inspiratory capacity increased the mixing time of the reactor was shortened. Thus the air input was beneficial for the fluid mixing. During the three phases mixing process, the mixing time of the reactor could be decreased by the n increase of carrier and air loading together, but the change was not significant. The parameters affecting the reactor fluid state were fluid velocity, inspiratory capacity and carrier. KLa could be increased with the air loading increase, and at the same gas/liquid ratio when the pressure drop was high, KL~ value was increased. The amount of carrier complex influence on KLa. As the carrier loading continued to increase, its value had been dropped but the changes was not significant, and optimization condition was found at above 800 1 000 g carrier loading （pouzzolane） or 600 g PVC. Under gas/liquid ratio of 0.8% -5.2%, KLa was （0.62-1.37）×10^-2· s^-1.     

Characteristics of high-level youth soccer players: variation by playing position

The present study aimed to investigate positional differences in 744 high-level soccer players, aged 8 to 18 years. Players were assigned to six age groups (U9–U19) and divided into four playing positions (goalkeeper (GK), defender (DEF), midfielder (MF) and attacker (ATT)). MANOVA and effect sizes were used to examine anthropometrical and functional characteristics between all positions in all age groups. The main findings of the study were that GKs and DEFs were the tallest and heaviest compared with MFs and ATTs in all age groups. Further, between U9–U15, no significant differences in functional characteristics were found, except for dribbling skill, which MFs performed the best. In the U17–U19 age groups, ATTs seemed to be the most explosive (with GKs), the fastest and the more agile field players. These results suggest that inherent physical capacities (i.e., speed, power, agility) might select players in or reject players from an attacking position, which is still possible from U15–U17. Apparently, players with excellent dribbling skills at younger age are more likely to be selected to play as a MF, although, one might conclude that the typical physical characteristics for different positions at senior level are not yet fully developed among young soccer players between 8 and 14 years.