关于正态总体抽样分布定理的证明和思考

用数学归纳法,对正态总体抽样分布中的两个定理给出了一种简单的证明,以期为概率论与数理统计的有效教学提供借鉴.     

The etiology of mathematical self-evaluation and mathematics achievement: understanding the relationship using a cross-lagged twin study from age 9 to 12

The genetic and environmental origins of individual differences in mathematical self-evaluation over time and its association with later mathematics achievement were investigated in a UK sample of 2138 twin pairs at ages 9 and 12. Self-evaluation indexed how good children think they are at mathematical activities and how much they like those activities. Mathematics achievement was assessed by teachers based on UK National Curriculum standards. At both ages self-evaluation was approximately 40% heritable, with the rest of the variance explained by non-shared environment. The results also suggested moderate reciprocal associations between self-evaluation and mathematics achievement across time, with earlier self-evaluation predicting later performance and earlier performance predicting later self-evaluation. These cross-lagged relationships were genetically rather than environmentally mediated.     

Comparing active delay and procrastination from a self-regulated learning perspective

Researchers have proposed that the act of postponing academic work may be divided into a traditional definition of procrastination, viewed as maladaptive, and adaptive forms of delay. Adaptive forms of delay may be more consistent with certain facets of self-regulated learning. The current study investigated this issue by examining whether the relations between aspects of self-regulated learning and active delay may be distinct from the relations these aspects of self-regulated learning have with procrastination. Among 206 undergraduates, procrastination was positively predicted by mastery-avoidance goals and negatively by metacognitive strategy usage, whereas active delay was negatively predicted by avoidance goals and positively by self-efficacy. Furthermore, students who reported higher levels of active delay also received better grades. These findings provide support that active delay is a distinct form of delay from procrastination that may be more positive due to its associations with some adaptive self-regulatory processes and academic achievement.     

Relations of Children's Effortful Control and Teacher-Child Relationship Quality to School Attitudes in a Low-Income Sample

RESEARCH FINDINGS: The purpose of this study was to examine the relations of children's effortful control and quality of relationships with teachers to school attitudes longitudinally in an ethnically diverse and economically disadvantaged sample. Data were collected as part of a larger intervention project during mid-fall, winter, and late spring (ns = 823, 722, and 758, respectively) for 2 cohorts of 3- to 5-year-olds (collected during 2 different school years). Children's effortful control was assessed in the fall with parents' and teachers' reports and 2 behavioral measures. Teacher-child relationship quality was assessed mid-year with teachers' reports of closeness and conflict. Attitudes toward school were assessed in late spring using teachers' and students' reports of school avoidance and liking. Effortful control, in general, was positively correlated with teacher-child closeness and school liking and negatively correlated with conflict and school avoidance. Using structural equation modeling and controlling for sex and ethnicity, we found that effortful control was positively related to teacher-child relationship quality, which in turn was positively related to school attitudes. Furthermore, the relation of effortful control to school attitudes was mediated by teacher-child relationship quality. PRACTICE OR POLICY: Results provide evidence for the importance of relational processes that take place within the classroom context and have implications for teachers and clinicians working to increase school success in ethnic minority and low-income children.     

The design of motivational agents and avatars

While the addition of an anthropomorphic interface agent to a learning system generally has little direct impact on learning, it potentially has a huge impact on learner motivation. As such agents become increasingly ubiquitous on the Internet, in virtual worlds, and as interfaces for learning and gaming systems, it is important to design them to optimally impact motivation. The focus of this paper is on the design of agents and avatars (one’s self-representation as a visual agent) for enhancing motivational and affective outcomes, such as improving self-efficacy, engagement and satisfaction, moderating frustration, and/or improving stereotypes. Together with motivational messages and dialogue (which are not discussed here), the agent’s appearance is the most important design feature as it dictates the learner’s perception of the agent as a virtual social model, in the Bandurian sense. The message delivery, through a human-like voice with appropriate and relevant emotional expressions, is also a key motivational design feature. More research is needed to determine the specifics with respect to the ideal agent voice and the role of other nonverbal communication (e.g., deictic gestures) that may contribute to the agent’s role as an embodied motivator, particularly in the long-term.     

If We Teach Them, They Can Learn: Young Students Views of Nature of Science During an Informal Science Education Program

There have been substantial reform efforts in science education to improve students’ understandings of science and its processes and provide continual support for students becoming scientifically literate (AAAS, Benchmarks for science literacy, Oxford University Press, New York, 1993; NRC, National Academy Press, Washington, DC, 1996; NSTA, NSTA position statement: The nature of science, , 2000). Despite previous research, it is still unclear whether young children are actually developmentally ready to conceptualize the ideas that are recommended in the reforms (Akerson and Volrich, J Res Sci Teach 43:377–394, 2006). The purpose of this study was to explore how explicit-reflective instruction could improve young students’ understanding of NOS. During an informal education setting, the authors taught NOS aspects using explicit-reflective instruction. Overall the students participating in the program improved their understanding of the target aspects of NOS through use of explicit reflective instruction. However, the levels of improvement varied across different aspects. Students improved the most in their understanding of the tentative nature of science and the roles of observation in scientific work, although there was still some confusion regarding the distinction between observation and inference. More work needs to be done exploring these specific topics and the role explicit reflective practice can play in identifying the particular problems students have in distinguishing these constructs.     

Inexpensive Options for a High-Tech Learning Environment

Radford University was recently configured with a campus-wide wireless local area network. Using these new capabilities, a classroom-based Honors section of Concepts of Biology was conducted solely using electronic technologies (paper was never transferred from professor to student). To accomplish this, students used common software and freeware. Commercial versions of similar software are designed solely for academic use, however, here the students were trained to use software and technologies that will be available to them once leaving the institution. Overall, students in this course responded favorably to the use of technology and reported that it aided in their learning process.     

Mode of communication, perceived level of understanding, and perceived quality of life in youth who are deaf or hard of hearing

Given the important role of parent-youth communication in adolescent well-being and quality of life, we sought to examine the relationship between specific communication variables and youth perceived quality of life in general and as a deaf or hard-of-hearing (DHH) individual. A convenience sample of 230 youth (mean age = 14.1, standard deviation = 2.2; 24% used sign only, 40% speech only, and 36% sign + speech) was surveyed on communication-related issues, generic and DHH-specific quality of life, and depression symptoms. Higher youth perception of their ability to understand parents' communication was significantly correlated with perceived quality of life as well as lower reported depressive symptoms and lower perceived stigma. Youth who use speech as their single mode of communication were more likely to report greater stigma associated with being DHH than youth who used both speech and sign. These findings demonstrate the importance of youths' perceptions of communication with their parents on generic and DHH-specific youth quality of life.     

The Importance of Teaching and Learning Nature of Science in the Early Childhood Years

Though research has shown that students do not have adequate understandings of nature of science (NOS) by the time they exit high school, there is also evidence that they have not received NOS instruction that would enable them to develop such understandings. How early is “too early” to teach and learn NOS? Are students, particularly young students, not capable of learning NOS due to developmental unreadiness? Or would young children be capable of learning about NOS through appropriate instruction? Young children (Kindergarten through third grade) were interviewed and taught about NOS in a variety of contexts (informal, suburban, and urban) using similar teaching strategies that have been found effective at teaching about NOS with older students. These teaching strategies included explicit decontextualized and contextualized NOS instruction, through the use of children’s literature, debriefings of science lessons, embedded written NOS assessments, and guided inquiries. In each context the researchers interviewed students prior to and after instruction, videotaped science instruction and maintained researcher logs and field notes, collected lesson plans, and copies of student work. The researchers found that in each setting young children did improve their understandings of NOS. Across contexts there were similar understandings of NOS aspects prior to instruction, as well as after instruction. There were also several differences evident across contexts, and across grade levels. However, it is clear that students as young as kindergarten are developmentally capable of conceptualizing NOS when it is taught to them. The authors make recommendations for teaching NOS to young children, and for future studies that explore learning progressions of NOS aspects as students proceed through school.