Density histograms can bridge the gap between histograms and continuous probability distributions, but research on how to learn and teach them is scarce. In this paper, we explore the learning of density histograms with the research question: How can a sequence of tasks designed from an embodied instrumentation perspective support students’ understanding of density histograms? Through a sequence of tasks based on students’ notions of area, students reinvented unequal bin widths and density in histograms. The results indicated that students had no difficulty choosing bin widths or using area in a histogram. Nevertheless, reinvention of the vertical density scale required intense teacher intervention suggesting that in future designs, this scale should be modified to align with students’ informal notions of area. This study contributes to a new genre of tasks in statistics education based on the design heuristics of embodied instrumentation.
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Many students persistently misinterpret histograms. This calls for closer inspection of students’ strategies when interpreting histograms and case-value plots (which look similar but are diferent). Using students’ gaze data, we ask: How and how well do upper secondary pre-university school students estimate and compare arithmetic means of histograms and case-value plots? We designed four item types: two requiring mean estimation and two requiring means comparison. Analysis of gaze data of 50 students (15–19 years old) solving these items was triangulated with data from cued recall. We found five strategies. Two hypothesized most common strategies for estimating means were confirmed: a strategy associated with horizontal gazes and a strategy associated with vertical gazes. A third, new, count-and-compute strategy was found. Two more strategies emerged for comparing means that take specific features of the distribution into account. In about half of the histogram tasks, students used correct strategies. Surprisingly, when comparing two case-value plots, some students used distribution features that are only relevant for histograms, such as symmetry. As several incorrect strategies related to how and where the data and the distribution of these data are depicted in histograms, future interventions should aim at supporting students in understanding these concepts in histograms. A methodological advantage of eye-tracking data collection is that it reveals more details about students’ problem-solving processes than thinking-aloud protocols. We speculate that spatial gaze data can be re-used to substantiate ideas about the sensorimotor origin of learning mathematics.
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Poster presented at the 14th Congress of the European Society for Research in Mathematics Education, Free University of Bozen-Bolsano, Italy.
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Reducing the use of pesticides by early visual detection of diseases in precision agriculture is important. Because of the color similarity between potato-plant diseases, narrow band hyper-spectral imaging is required. Payload constraints on unmanned aerial vehicles require reduc- tion of spectral bands. Therefore, we present a methodology for per-patch classification combined with hyper-spectral band selection. In controlled experiments performed on a set of individual leaves, we measure the performance of five classifiers and three dimensionality-reduction methods with three patch sizes. With the best-performing classifier an error rate of 1.5% is achieved for distinguishing two important potato-plant diseases.
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Purpose: To establish age-related, normal limits of monocular and binocular spatial vision under photopic and mesopic conditions. Methods: Photopic and mesopic visual acuity (VA) and contrast thresholds (CTs) were measured with both positive and negative contrast optotypes under binocular and monocular viewing conditions using the Acuity-Plus (AP) test. The experiments were carried out on participants (age range from 10 to 86 years), who met pre-established, normal sight criteria. Mean and ± 2.5σ limits were calculated within each 5-year subgroup. A biologically meaningful model was then fitted to predict mean values and upper and lower threshold limits for VA and CT as a function of age. The best-fit model parameters describe normal aging of spatial vision for each of the 16 experimental conditions investigated. Results: Out of the 382 participants recruited for this study, 285 participants passed the selection criteria for normal aging. Log transforms were applied to ensure approximate normal distributions. Outliers were also removed for each of the 16 stimulus conditions investigated based on the ±2.5σ limit criterion. VA, CTs and the overall variability were found to be age-invariant up to ~50 years in the photopic condition. A lower, age-invariant limit of ~30 years was more appropriate for the mesopic range with a gradual, but accelerating increase in both mean thresholds and intersubject variability above this age. Binocular thresholds were smaller and much less variable when compared to the thresholds measured in either eye. Results with negative contrast optotypes were significantly better than the corresponding results measured with positive contrast (p < 0.004). Conclusions: This project has established the expected age limits of spatial vision for monocular and binocular viewing under photopic and high mesopic lighting with both positive and negative contrast optotypes using a single test, which can be implemented either in the clinic or in an occupational setting.
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In order to achieve a level of community involvement and physical independence, being able to walk is the primary aim of many stroke survivors. It is therefore one of the most important goals during rehabilitation. Falls are common in all stages after stroke. Reported fall rates in the chronic stage after stroke range from 43 to 70% during one year follow up. Moreover, stroke survivors are more likely to become repeated fallers as compared to healthy older adults. Considering the devastating effects of falls in stroke survivors, adequate fall risk assessment is of paramount importance, as it is a first step in targeted fall prevention. As the majority of all falls occur during dynamic activities such as walking, fall risk could be assessed using gait analysis. It is only recent that technology enables us to monitor gait over several consecutive days, thereby allowing us to assess quality of gait in daily life. This thesis studies a variety of gait assessments with respect to their ability to assess fall risk in ambulatory chronic stroke survivors, and explores whether stroke survivors can improve their gait stability through PBT.
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Crowdfunding is gaining popularity as a viable means to raise financial capital for good causes, cultural goods, new products, and ventures. Little empirical research has been done to understand crowdfunding and basic academic knowledge of its dynamics is still lacking. By data mining the crowdfunding platform Kickstarter.com and Facebook we collected a large dataset of crowdfunding projects and the ego networks of the entrepreneurs. We study the relation of the success of the Kickstarter project to his social network and to media activities and find a scaling law that predicts the number of clicks on the project website required for a successful project. Examining the results of the social network analysis we concluded that successful initiators on Kickstarter have more friends but a sparser network. Unsuccessful entrepreneurs on the other hand have a higher average degree suggesting a denser network. Our analyses suggest that sparse, and thus diverse networks are beneficial for the success of a project.
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Airborne wind energy (AWE) is an emerging renewable energy technology that uses kites to harvest winds at higher altitudes than wind turbines. Understanding how residents experience a local AWE system (AWES) is important as the technology approaches commercialization. Such knowledge can help adjust the design and deployment of an AWES to fit locals' needs better, thereby decreasing the technology's burden on people. Although the AWE literature claims that the technology affects nature and residents less than wind turbines, empirical evidence has been lacking. This first community acceptance study recruited residents within a 3.5 km radius of an AWE test site in Northern Germany. Using structured questionnaires, 54 residents rated the AWES and the closest wind farm on visual, sound, safety, siting, environmental, and ecological aspects. Contrary to the literature's claims, residents assessed the noise, ecological, and safety impacts similarly for the AWES and the wind farm. Only visual impacts were rated better for the AWES (e.g., no shadows were perceived). Consistent with research on wind turbines, residents who rated the site operation as fairer and the developer as more transparent tended to have more positive attitudes towards the AWES and to experience less noise annoyance. Consequently, recommendations for the AWE industry and policymakers include mitigating technology impacts and implementing evidence-based strategies to ensure just and effective project development. The findings are limited to one specific AWES using soft-wing kites. Future research should assess community responses across regions and different types of AWESs to test the findings' generalizability.
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Validity and Reproducibility of a New Treadmill Protocol: The Fitkids Treadmill Test. Med. Sci. Sports Exerc., Vol. 47, No. 10, pp. 2241–2247, 2015. Purpose: This study aimed to investigate the validity and reproducibility of a new treadmill protocol in healthy children and adolescents: the Fitkids Treadmill Test (FTT). Methods: Sixty-eight healthy children and adolescents (6–18 yr) were randomly divided into a validity group (14 boys and 20 girls; mean T SD age, 12.9 T 3.6 yr) that performed the FTT and Bruce protocol, both with respiratory gas analysis within 2 wk, and a reproducibility group (19 boys and 15 girls; mean T SD age, 13.5 T 3.5 yr) that performed the FTT twice within 2 wk. A subgroup of 21 participants within the reproducibility group performed both FTT with respiratory gas analysis. Time to exhaustion (TTE) was the main outcome of the FTT. Results: V˙ O2peak measured during the FTT showed excellent correlation with V˙ O2peak measured during the Bruce protocol (r = 0.90; P G 0.01). Backward multiple regression analysis provided the following prediction equations for V˙ O2peak (LIminj1) for boys and girls, respectively: V˙ O2peak FTT ¼ j0:748 þ ð0:117 TTEFTTÞ þ ð0:032 bodymassÞ þ 0:263, and V˙ O2peak FTT ¼ j0:748 þ ð0:117 TTEFTTÞ þ ð0:032 bodymassÞ [R2 ¼ 0:935; SEE ¼ 0:256LI min j1]. Cross-validation of the regression model showed an R2 value of 0.76. Reliability statistics for the FTT showed an intraclass correlation coefficient of 0.985 (95% confidence interval, 0.971–0.993; P G 0.001) for TTE. Bland–Altman analysis showed a mean bias of j0.07 min, with limits of agreement between +1.30 and j1.43 min. Conclusions: Results suggest that the FTT is a useful treadmill protocol with good validity and reproducibility in healthy children and adolescents. Exercise performance on the FTT and body mass can be used to adequately predict V˙ O2peak when respiratory gas analysis is not available.
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Background. Recent research has shown that the Fitkids Treadmill Test (FTT) is a valid and reproducible exercise test for the assessment of aerobic exercise capacity in children and adolescents who are healthy. Objective. The study objective was to provide sex- and age-related normative values for FTT performance in children and adolescents who were healthy, developing typically, and 6 to 18 years of age. Design. This was a cross-sectional, observational study. Methods. Three hundred fifty-six children and adolescents who were healthy (174 boys and 182 girls; mean age12.9 years, SD3.7) performed the FTT to their maximal effort to assess time to exhaustion (TTE). The least-mean-square method was used to generate sex- and age-related centile charts (P3, P10, P25, P50, P75, P90, and P97) for TTE on the FTT. Results. In boys, the reference curve (P50) showed an almost linear increase in TTE with age, from 8.8 minutes at 6 years of age to 16.1 minutes at 18 years of age. In girls, the P50 values for TTE increased from 8.8 minutes at 6 years of age to 12.5 minutes at 18 years of age, with a plateau in TTE starting at approximately 10 years of age. Limitations. Youth who were not white were underrepresented in this study. Conclusions. This study describes sex- and age-related normative values for FTT performance in children and adolescents who were healthy, developing typically, and 6 to 18 years of age. These age- and sex-related normative values will increase the usefulness of the FTT in clinical practice.
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