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We conducted surveys of adults participating in municipally sponsored volunteer events in the Portland, OR metropolitan area in order to understand the range of attitudes and behaviors associated with volunteer work. We sampled 172 individuals in 18 events from February to June 2012. Principal components and factor analyses of survey responses identified three groups based on annual frequency of participation in stewardship events: first-time volunteers, mid-level volunteers (3–10 events per year), and frequent volunteers (>10 events per year). Our analyses revealed three main factors that explained the variation in survey response for the three volunteer groups: environmental identity, private pro-environmental behavior, and civic engagement. All three factors were positively correlated with frequency of participation in stewardship events, with the most frequent volunteers indicating the highest degree of attention to environmental issues, environmental identity, and self-reported pro-environmental behaviors. Frequent volunteers were more likely to feel personally attached to their local environment, believe that their efforts help solve environmental problems, and enjoy being part of community efforts. These results suggest that stewardship activities provide opportunities for volunteers to interact with others while working collectively toward restoring and maintaining parks, which may contribute to more resilient communities.  相似文献   
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Binocular disparity provides one of the important depth cues within stereoscopic three-dimensional (3D) visualization technology. However, there is limited research on its effect on learning within a 3D augmented reality (AR) environment. This study evaluated the effect of binocular disparity on the acquisition of anatomical knowledge and perceived cognitive load in relation to visual-spatial abilities. In a double-center randomized controlled trial, first-year (bio)medical undergraduates studied lower extremity anatomy in an interactive 3D AR environment either with a stereoscopic 3D view (n = 32) or monoscopic 3D view (n = 34). Visual-spatial abilities were tested with a mental rotation test. Anatomical knowledge was assessed by a validated 30-item written test and 30-item specimen test. Cognitive load was measured by the NASA-TLX questionnaire. Students in the stereoscopic 3D and monoscopic 3D groups performed equally well in terms of percentage correct answers (written test: 47.9 ± 15.8 vs. 49.1 ± 18.3; P = 0.635; specimen test: 43.0 ± 17.9 vs. 46.3 ± 15.1; P = 0.429), and perceived cognitive load scores (6.2 ± 1.0 vs. 6.2 ± 1.3; P = 0.992). Regardless of intervention, visual-spatial abilities were positively associated with the specimen test scores (η2 = 0.13, P = 0.003), perceived representativeness of the anatomy test questions (P = 0.010) and subjective improvement in anatomy knowledge (P < 0.001). In conclusion, binocular disparity does not improve learning anatomy. Motion parallax should be considered as another important depth cue that contributes to depth perception during learning in a stereoscopic 3D AR environment.  相似文献   
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Sample size can be chosen to achieve a specified width in a confidence interval. The probability of obtaining a narrow width given that the confidence interval includes the population parameter is defined as the power of the confidence interval, a concept unfamiliar to many practitioners. This article shows how to utilize the Statistical Analysis System (SAS) proc power procedure to determine an appropriate sample size and achieve sufficient power for a specified confidence interval. Two examples in sport and exercise science are used to illustrate sample size determination for confidence intervals in the dependent and independent t tests. The relevant SAS code and output are provided with detailed annotations. As the use of confidence intervals becomes a more integral part of studies in sport and exercise science, the reporting and analysis of their power should be considered much like that of hypothesis tests.  相似文献   
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