Not quite normal: Consequences of violating the assumption of normality in regression mixture models     

Lee Van Horn M  Smith J  Fagan AA  Jaki T  Feaster DJ  Masyn K  Hawkins JD  Howe G 《Structural equation modeling》2012,19(2):227-249

Regression mixture models are a new approach for finding differential effects which have only recently begun to be used in applied research. This approach comes at the cost of the assumption that error terms are normally distributed within classes. The current study uses Monte Carlo simulations to explore the effects of relatively minor violations of this assumption, the use of an ordered polytomous outcome is then examined as an alternative which makes somewhat weaker assumptions, and finally both approaches are demonstrated with an applied example looking at differences in the effects of family management on the highly skewed outcome of drug use. Results show that violating the assumption of normal errors results in systematic bias in both latent class enumeration and parameter estimates. Additional classes which reflect violations of distributional assumptions are found. Under some conditions it is possible to come to conclusions that are consistent with the effects in the population, but when errors are skewed in both classes the results typically no longer reflect even the pattern of effects in the population. The polytomous regression model performs better under all scenarios examined and comes to reasonable results with the highly skewed outcome in the applied example. We recommend that careful evaluation of model sensitivity to distributional assumptions be the norm when conducting regression mixture models.  相似文献   

Learning to solve problems     

David H. Jonassen  Erika R. Gilmore 《Performance Improvement》2005,44(9):45-47

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The question book goes interactive     

Robert W. Bauer  Sandra S. Bauer  Erika R. Gilmore 《Performance Improvement》2004,43(4):45-47

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The European dilemma: evaluating the implications of UEFA Europa League participation on English Premier League clubs     

Adam Cox  Sarah Gilmore 《Soccer & Society》2017,18(7):817-835

For clubs qualifying for the UEFA Europa League, participation generates a series of tensions. UEFA has provided financial rewards for those clubs, but with qualification comes additional pressures on playing squads which are often less able to deal with the performative demands of an extra competition, as they generally possess fewer financial resources compared with teams gaining Champions League qualification. This paper evaluates these conflicting tensions. The study takes a detailed quantitative analysis of the costs and benefits for four Premier League clubs that have repeatedly participated in the Europa League over eight seasons. It demonstrates a positive financial benefit of participation, but this is only significant if the club progresses to the later competition stages and has a robust playing squad. This research fills a gap in a lack of analysis based on reliable empirical data as to the impact of participation in this competition on clubs.  相似文献   

‘Partnership’ in Action: Contagious Abortion and the Governance of Livestock Disease in Britain, 1885–1921     

Abigail Woods 《Minerva》2009,47(2):195-216

Most histories of livestock disease in Britain treat the development of control policy as a government responsibility, to which farmers made little constructive contribution. Similarly, farmers rarely appear in accounts of disease research. This paper uses the example of contagious abortion (brucellosis) at the turn of the twentieth century to reveal that state-farming collaboration in research and policy did in fact occur, and that it operated in various ways, with often unexpected outcomes. The collaborative approach to contagious abortion is partly attributed to its clinical and epidemiological features, which made it an unsuitable candidate for the existing, state-led policy of stamping out disease. It is claimed that such collaboration has been overlooked by historians on account of their focus upon diseases that were amenable to stamping out. This focus needs to change if history is to inform present-day disease governance in Britain, which is founded on the concept of ‘partnership’ between farmers and the state.

Abigail WoodsEmail:

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The effects of impact and non-impact exercise on circulating markers of collagen remodelling in humans     

Mackey AL  Donnelly AE  Swanton A  Murray F  Turpeenniemi-Hujanen T 《Journal of sports sciences》2006,24(8):843-848

Exercise has been shown to influence collagen synthesis and degradation. The aim of this study was to determine whether the stimulus for these changes is metabolic or mechanical. Eight healthy adults aged 22 +/- 4 years (mean +/- s) completed two exercise bouts-a 10 km road run and a deep water running session. Blood samples were collected before exercise and on days 1, 2, 3, 6 and 10 after exercise for measurement of creatine kinase activity, type IV collagen antigenicity, and concentrations of matrix metalloproteinase (MMP)- 9, tissue inhibitors of metalloproteinase (TIMP)- 1 and -2, and the MMP-2/TIMP-2 complex. Serum creatine kinase was elevated 24 h after the road run, but unchanged after the deep water running session. Serum collagen IV antigenicity decreased after both the road run and the deep water running session, suggesting suppressed type IV collagen synthesis in response to exercise, although serum MMPs and TIMPs remained unchanged after exercise. These results suggest that collagen IV synthesis is temporarily suppressed after exercise, irrespective of exercise type.  相似文献   

The Effects of Concreteness on Mathematical Manipulative Choice     

Megan Foulkes  Francesco Sella  Theresa Elise Wege  Camilla Gilmore 《Mind, Brain, and Education》2023,17(3):185-196

There is mixed evidence as to whether concrete manipulatives (e.g., toy animals) are better than abstract manipulatives (e.g., counters) for teaching mathematical concepts to children. Concreteness is defined as the amount of extraneous information a manipulative provides, and in this study we aimed to unpick which dimensions of concreteness influence manipulative choice. Researchers, teachers, and parents completed a comparative judgment task comparing images of manipulatives varying in different dimensions of concreteness, selecting which they would choose to teach arithmetic to children. The findings indicated homogeneous, 3-dimensional manipulatives were the most preferred across all groups to teach arithmetic to children, regardless of more extraneous features. This contradicts research recommendations to minimize the use of concrete manipulatives due to their distractive qualities. Instead, it suggests that some concrete features may be preferred in more naturalistic contexts. More research is required to investigate how different dimensions of concreteness influence learning outcomes for children both in artificial research contexts and in practice.  相似文献