Dissecting the Impact of DIF/DBF on Ability Estimation and Person Fit

Prior research has shown that differential item functioning (DIF) and differential bundle functioning (DBF) can influence ability estimation in unidimensional item repose theory (IRT); however, the relationship between ability estimation and uniform and non-uniform DIF/DBF has not been thoroughly investigated. Therefore, a simulation study was conducted to more thoroughly investigate how DIF/DBF and other related factors influence ability estimation in IRT. The factors examined included bundle size, the sum of uniform DIF in a bundle, magnitude of non-uniform DIF in each item in a bundle, balance of reference and focal group examinees, test length, and impact. Results indicated that an increase in uniform DIF/DBF leads to positive ability estimation bias for reference group examinees ability estimates. The magnitude of non-uniform DIF/DBF was found to influence the root mean squared error (RMSE) of ability estimates and standard error of the estimates. Specifically, lower RMSE and lower standard errors were obtained when items were simulated to be more discriminating for the reference group. Rank order correlations between true and estimated ability were found to be highly consistent regardless of the magnitude of uniform and non-uniform DIF/DBF in the bundle. Finally, Crossing SIBTEST was found to provide acceptable type-I error rates and power when uniform DBF was simulated

“I’m Not a Traditional Teacher Anymore”: Ecuadoran Teacher Perspectives Regarding a US Professional Development Program

In this dissertation, the retrospective perspectives of five Ecuadoran English teachers regarding their experience in a seven-month professional development program in the US were investigated. Attention was given to how they believed the program impacted their identity, self-efficacy and how they perceived the program functioned as a community of practice (CoP). Data were collected through interviews using stimulated recall based on classrooms observation notes and memos in the teacher participants’ Ecuadoran schools. Findings included that the Ecuadoran teachers felt they were positively impacted by the program. They perceived themselves as more legitimate speakers of English and more effective educators; however, there were areas in which they believed the program did not meet their needs. The five teachers perceived that the program was frequently not contextualized for the Ecuadoran system of education. Additionally, none of the five teacher participants believed that there was a collective CoP; however, four of the five teacher initiated small communities of practice, which they felt were significant in their success in the program. Once back in their Ecuadoran schools, these five teachers created small CoP with their colleagues and in their classrooms. The fifth Ecuadoran teacher believed that his Kichwa identity was not understood within the context of the program and that this inhibited his inclusion into any community

Building, Deploying and Operating a Cubesat Constellation - Exploring the Less Obvious Reasons Space is Hard

“Space is hard” often gets translated to “Space technology is hard”. This mindset disregards some of the critical aspects of developing, deploying and operating a Cubesat constellation. Throughout this paper, we walk through what Spire has undertaken to get a commercial satellite constellation up and running. To enable both scale and rapid technology iteration, the design processes and systems have evolved to be lean but reliable. An iterative systems engineering approach ensures the necessary control, speed and reliability as features are added to the constellation. Solid process control and an experienced manufacturing team ensure reliable, repeatable and rapid satellite Assembly, Integration and Testing (AIT). A global groundstation network provides full control in accessing the satellite data. Complex software systems are in place to orchestrate the space and ground assets, to extract maximum customer value and provide the mission flexibility that’s needed in rapidly changing market environments. An efficient satellite operations team monitors and responds to the changing behaviors of the constellation. All of these factors together comprise a system that can be leveraged to enable other businesses to be successful as well without having to build and maintain all this infrastructure, as the importance of the space-as-a-service concept grows

Relationship of resting and submaximal cardiovascular measures to VO[2]max in untrained children

Participation by children in organized sport continues to increase. A 1994 survey of 10,000 households by the National Sporting Goods Association (1994) found that approximately 40,000 children between the ages of 7-17 years participate in an organized sport or recreational activity annually. In the realm of organized sports, especially endurance activities, there continues to be interest in how cardiovascular fitness is attained and how it can be maximized. Measurement of cardiovascular fitness is an important piece to that puzzle. The most common and most descriptive measure for children and adults, is the maximal oxygen uptake or max (Astrand & Rodahl, 1977, p.318; Bar-Or, 1983, p.3; McArdle et al., 1994, p. 125; Pollock, 1973). This refers specifically to the amount of oxygen required by the cells to produce energy for physical work at the body’s maximal level (McArdle et al., 1994, p.66). Individual components of max are cardiac output (consisting of stroke volume and heart rate) and the arterio-venous oxygen difference (see Definition of Terms). It seems therefore, that an improvement in the efficiency of any of these factors would improve max and, in turn, cardiovascular fitness levels. The relationship between cardiovascular fitness and each of its’ individual components has been extensively reviewed for adults (American College of Sports Medicine, 1990; Andrew et al., 1966; Astrand &Rodahl, 1977, p.394; Clausen, 1977; Pollock, 1973; Rowell, 1986; Saltin, 1990; Scheuer & Tipton, 1977). The frequency, intensity and duration of exercise necessary for improving maximal oxygen consumption and therefore cardiovascular fitness for adults is also well established (American College of Sports Medicine, 1990; Pollock, 1973). The type of endurance training recommended to improve max (American College of Sports Medicine, 1990) causes adaptions in all the previously mentioned components of maximal submaximal and maximal exercise (Andrew et al., 1966; Astrand & Rodahl, 1977, p.394; Clausen, 1977; McArdle et al., 1994, p.263-264; Rowell, 1986; Saltin, 1990; Scheuer & Tipton, 1977). A decrease in the heart rate at rest and during submaximal exercise has also been reported and is considered a hallmark of aerobic fitness (American College of Sports Medicine, 1990; Andrew et al., 1966; Astrand &Rodahl, 1977, p.394; McArdle et al., 1994, p.366; Saltin, 1990; Scheuer, 1977). The decrease in heart rate associated with endurance training is related to stroke volume increases to support the increase in cardiac output during exercise and to maintain cardiac output at rest (Astrand &Rodahl, 1977, p.394; Clausen, 1977; McArdle et al., 1994, p.264; Rowell, 1986; Saltin, 1990; Scheuer & Tipton, 1977). Increases in arterio-venous oxygen difference have also been found to occur with endurance training in adults (Andrew et al., 1966; Astrand &Rodahl, 1977, p.394; Clausen, 1977; McArdle et al., 1994, p.366; Pollock, 1973; Rowell, 1986; Saltin, 1990; Scheuer & Tipton, 1977). Additional anatomical and physiological changes in the structure and function of the heart itself are improvements in the myocardial thickness, left ventricular volume, and thus cardiac contractility that occurs with endurance training in adults (Adams, 1978; Demaria et al., 1978; Ehsani, et al., 1978; Gilbert et al., 1977; McArdle et al., 1994, p.366)

Happy or SAD? Quaking Aspen (\u3cem\u3ePopulus tremuloides\u3c/em\u3e Michx.) on Cedar Mountain, Southern Utah

Quaking aspen forests are important communities in the western United States where they provide preferential food and habitat for animals, limit wildfires from spreading, and have favorable aesthetics, among other things. Their putative decline is an issue for ecology and management. We remeasured the aspen population on Cedar Mountain, Utah, to assess changes to its condition since it was originally surveyed in 2008. We found that the area comprised of stable aspen (\u3e80% aspen) decreased from 84.3% to 69.7%. The amount of mortality has increased slightly over the last decade, but crown dieback has stayed virtually identical. Additionally, the intensity and frequency of insect and pathogen damage have increased significantly. The amount of aspen in the understory has increased, resulting in more of the landscape exhibiting levels of regeneration sufficient for aspen to be self-replacing. While the ratio of overstory to understory aspen was identical between sampling periods, the amount of sapling-sized trees recruiting to the overstory increased. The extent of browsing of understory aspen has also decreased. Extant aspen forests are increasing in age, and relative density indicates the landscape is further senescing. If the amount of aspen mortality is not matched or surpassed by the amount of regeneration and recruitment, the aspen forest type will likely continue to reduce in area and/or be converted to conifer forest or non-forested land. Measuring and assessing changes to the structure, composition, crown condition, mortality, damage presence, regeneration and recruitment level, and browsing pressure of this aspen population improves our understanding of potential causes and factors involved in reductions to aspen forests in southern Utah. This understanding can inform aspen forest management and provide insight into aspen forest dynamics, generally

I\u27m not a traditional teacher anymore : Ecuadoran teacher perspectives regarding a US professional development program

In this dissertation, the retrospective perspectives of five Ecuadoran English teachers regarding their experience in a seven-month professional development program in the US were investigated. Attention was given to how they believed the program impacted their identity, self-efficacy and how they perceived the program functioned as a community of practice (CoP). Data were collected through interviews using stimulated recall based on classrooms observation notes and memos in the teacher participants\u27 Ecuadoran schools. Findings included that the Ecuadoran teachers felt they were positively impacted by the program. They perceived themselves as more legitimate speakers of English and more effective educators; however, there were areas in which they believed the program did not meet their needs. The five teachers perceived that the program was frequently not contextualized for the Ecuadoran system of education. Additionally, none of the five teacher participants believed that there was a collective CoP; however, four of the five teacher initiated small communities of practice, which they felt were significant in their success in the program. Once back in their Ecuadoran schools, these five teachers created small CoP with their colleagues and in their classrooms. The fifth Ecuadoran teacher believed that his Kichwa identity was not understood within the context of the program and that this inhibited his inclusion into any community

SmallSat Manufacturing; The Spire Constant NPI Model

Producing 100 of anything in 1 year is not considered high volume in most businesses, but in the satellite manufacturing world it is, even if those satellites are 3U cubesats. The additional complications of a variable launch schedule and the need to launch the latest hardware drives a need for a robust but agile process. As with everything at Spire we are addressing this problem with an iterative approach to the 4 main requirements. These are not serially dependant steps, but a group of parallel iterations

TECHNIQUE CHARACTERISTICS OF ELITE BREASTSTROKE SWIMMERS

INTRODUCTION-There have been substantial changes in technique in breaststroke swimming following the introduction of the 'wave-action' technique. Due to continual experimentation by swimmers and coaches to find the technique that best suits each swimmer, the observable characteristics of elite swimmers vary considerably. The purpose of this study was to investigate the technique characteristics of elite breaststroke swimmers to identify and quantify aspects of technique that are common among elite swimmers and those which are variable. METHODS-Two above water and two below water cameras were used to obtain three-dimensional data from eight internationally elite breaststroke swimmers swimming in the 100m and 200m heats and finals of the 1992 Olympics in Barcelona. The swimmers were recorded while they passed between five and ten metres fram the turning end of the pool. The time histories of angles describing the orientation of the swimmer were determined using Peak Performance Technologies three-dimensional digitising and analysis software. The amplitude and frequency of waveforms comprising the vertical undulations of the body parts and the phase relationships between them were determined by Fourier analysis RESULTS-There was considerable variability among swimmers in the time histories of angular motions and in the amplitudes and phase relationships of the waveforms comprising the vertical undulations. In the case of all swimmers the vertical undulations of the vertex of the head and shoulders resembled simple sinusoidal waveforms with a frequency equivalent to that of the stroke cycle. The vertical undulations of the hips, knees, and ankles displayed large contributions by hlgher frequency components. The realtive magnitudes of these contributions varied considerably among swimmers. CONCLUSION-It was concluded that breaststroke swimmers use different techniques to achieve top performance