Children’s use of subtraction by addition on large single-digit subtractions

Subtractions of the type M − S = ? can be solved by various strategies, including subtraction by addition. In this study, we investigated children’s use of subtraction by addition by means of reaction time analyses. We presented 106 third to sixth graders with 32 large non-tie single-digit problems in both subtraction (12 − 9 = .) and addition format (9 + . = 12). We examined the fit of three regression models, which represented the consistent use of direct subtraction, of subtraction by addition and of flexibly switching between both strategies based on the relative size of the subtrahend. Findings revealed that children did not switch flexibly between the two strategies, as adults do, but that they rely on direct subtraction for problems presented in subtraction format and on subtraction by addition for problems in addition format. We end with the major theoretical, methodological and educational implications of these results.     

《孙子十家注》源流轨迹

《宋史·艺文志》著录吉天保《十家孙子会注》为《孙子十家注》的原始著录,其源则为各家注本的出现,其中依次包括曹操、孟氏、李筌、贾林、杜佑、杜牧、陈皋、何延锡、王晳、梅尧臣、张预十一家注。吉氏成书后重要的刊本则有:明正统《道藏》刊《孙子注解》;明谈恺、李棣、黄邦彦等刊《孙子集注》;清孙星衍刊《孙子十家注》;及1961年中华书局上海编辑所影刊的《宋本十一家注孙子》。     

Biomechanical analysis of the penalty-corner drag-flick of elite male and female hockey players

The aim of this study was to analyse the kinematic sequencing in the penalty-corner drag-flicks of elite male and female field hockey players of international calibre. Thirteen participants (one skilled male drag-flicker and six male and six female elite players) participated in the study. An optoelectronic motion analysis system was used to capture the drag-flicks with six cameras, sampling at 250 Hz. Select ground reaction force parameters were obtained from a force platform which registered the last support of the front foot. Twenty trials were captured from each subject. Both player groups showed significantly (p < 0.05) smaller ball velocity at release, peak angular velocity of the pelvis, and negative and positive peak angular velocities of the stick than the skilled subject. Normalised ground reaction forces of the gender groups were also smaller than that of the skilled drag-flicker. By comparing these players we established that the cues of the skill level are a wide stance, a whipping action (rapid back lift) of the stick followed by an explosive sequential movement of the pelvis, upper trunk and stick.     

Exploration of the Relative Contributions of Domain Knowledge and Search Expertise for Conducting Internet Searches

The relative contributions of expertise in search skills and domain knowledge were examined when using the Internet to find information. Four conditions were compared: expert searchers/high domain knowledge; expert searchers/low domain knowledge; novice searchers/high domain knowledge; and novice searchers/low domain knowledge. Search outcomes and verbal protocols were analyzed. The combination of search expertise and high domain knowledge yielded the most efficient searches. Higher search expertise yielded access to sites rated more accurate and credible. High domain knowledge yielded sites rated more thorough. Verbal protocols depicted searching as a complex decision process. Findings have implications for instructional support.     

A New Study on Educational Effectiveness in Secondary Schools in Flanders: An Introduction

As an introduction to the articles of Opdenakker, Van Damme, De Fraine, Van Landeghem, and Onghena (2002) and Van Landeghem, Van Damme, Opdenakker, De Fraine, and Onghena (2002) in this issue, we give some background information on a new study on educational effectiveness in secondary schools, and on the variables measured in that study that are relevant to the 2 articles mentioned. We conclude with some information on the system of secondary education in Flanders.     

School self-evaluation: self-perception or self-deception? The impact of motivation and socially desirable responding on self-evaluation results

ABSTRACT

In order to enhance the quality of education, school self-evaluation (SSE) has become a key strategy in many educational systems. During an SSE process, schools describe and evaluate their own functioning, often by administering questionnaires among teachers. However, it is unknown to what extent SSE questionnaire results are distorted by respondents’ tendencies towards socially desirable responding and their motivation to fill in an SSE questionnaire. This study reports on a path analysis, performed on the results of an authentic SSE with 382 participants. Results indicate that socially desirable responding and motivation have indeed an impact on SSE results. However, the effects are differential and depend on the variable of interest. These findings can have serious implications, and should be taken into account when drawing conclusions and taking (school) policy decisions within the framework of an SSE process.     

Understanding floating: A study of children aged between six and eight years

Graphs of real-time experiments are useful tools in science education; their intrinsic features allow innovative didactic approaches. The use of such images is spreading and is likely to become common classroom practice. This paper describes a study in which secondary school students were called upon to read and interpret documents containing images of real-time kinematics graphs specially designed to address common learning problems and to minimize iconic difficulties. Both novice students and those with a little experience of real-time experiments were involved. The overall didactic intentions of the presented documents were fulfilled. Some reading difficulties related to specific features were detected and are discussed. Suggestions are made regarding the acquisition of some specific capabilities that are needed to avoid misinterpreting these images and are of transversal value across several contexts. Finally, some implications for teacher training and class activities are discussed.     

Evaluating a Professional Development Framework to Empower Chemistry Teachers to Design Context-Based Education

Even experienced chemistry teachers require professional development when they are encouraged to become actively engaged in the design of new context-based education. This study briefly describes the development of a framework consisting of goals, learning phases, strategies and instructional functions, and how the framework was translated into a professional development programme intended to empower teachers to design context-based chemistry education. The programme consists of teaching a pre-developed context-based unit, followed by teachers designing an outline of a new context-based unit. The study investigates the process of teacher empowerment during the implementation of the programme. Data were obtained from meetings, classroom discussions and observations. The findings indicated that teachers became empowered to design new context-based units provided they had sufficient time and resources. The contribution of the framework to teacher empowerment is discussed.