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31.
A sample size justification should be given for all clinical investigations. However, sometimes the objective of a trial is to estimate an effect with a view to planning a later definitive study. This paper describes the calculations for designing studies where one wishes to adopt an estimation approach through using confidence intervals around the overall response. Calculations are given for data anticipated to take a Normal form. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
32.
Estimated associations between an outcome variable and misclassified covariates tend to be biased when the methods of estimation that ignore the classification error are applied. Available methods to account for misclassification often require the use of a validation sample (i.e. a gold standard). In practice, however, such a gold standard may be unavailable or impractical. We propose a Bayesian approach to adjust for misclassification in a binary covariate in the random effect logistic model when a gold standard is not available. This Markov Chain Monte Carlo (MCMC) approach uses two imperfect measures of a dichotomous exposure under the assumptions of conditional independence and non-differential misclassification. A simulated numerical example and a real clinical example are given to illustrate the proposed approach. Our results suggest that the estimated log odds of inpatient care and the corresponding standard deviation are much larger in our proposed method compared with the models ignoring misclassification. Ignoring misclassification produces downwardly biased estimates and underestimate uncertainty. 相似文献
33.
Professor Stephen Senn Dr Dipti Amin Professor Rosemary A. Bailey Professor Sheila M. Bird FFPH Dr Barbara Bogacka Mr Peter Colman Dr rew Garrett Professor rew Grieve Professor Sir Peter Lachmann FRS FMedSci 《Journal of the Royal Statistical Society. Series A, (Statistics in Society)》2007,170(3):517-579
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Has the image of Che Guevara lost its power to evoke radical politics in the face of pervasive commodification? The commercialization of this 1960s political icon has called into question the power of the market to shape collective memories. Meanwhile, antisystemic movements of the left continue to erect his image at protest events. In light of this contest over how Che Guevara is remembered, we investigate, using data from a survey of Spanish citizens, who is most likely to recall him. We find qualified support for the theory of generational imprinting—Che is more often recalled by those generations who saw him rise to prominence during their formative years, although prominent as a collective symbol rather than as a living person. Our results also corroborate the claim that historical figures or events are more salient for, and therefore more likely to be remembered by, some subgenerational units than others. Thus, although the younger generations are in general more likely than their elders to recall Che, he is most frequently remembered by the highly educated leftists who espouse postmaterialist and posttraditionalist values and identify more with their local regions than with the nation of Spain. These patterns suggest that, in contrast to the dire predictions of mass culture theorists, the memory of Che Guevara has become increasingly tied to markers of social, ethnic‐regional, and political identity. 相似文献
36.
Maximum likelihood estimation and goodness-of-fit techniques are used within a competing risks framework to obtain maximum likelihood estimates of hazard, density, and survivor functions for randomly right-censored variables. Goodness-of- fit techniques are used to fit distributions to the crude lifetimes, which are used to obtain an estimate of the hazard function, which, in turn, is used to construct the survivor and density functions of the net lifetime of the variable of interest. If only one of the crude lifetimes can be adequately characterized by a parametric model, then semi-parametric estimates may be obtained using a maximum likelihood estimate of one crude lifetime and the empirical distribution function of the other. Simulation studies show that the survivor function estimates from crude lifetimes compare favourably with those given by the product-limit estimator when crude lifetimes are chosen correctly. Other advantages are discussed. 相似文献
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For the past two decades there has been much debate about the future of family farming. The basic question on which this debate has turned is whether current pressures on family farm systems should be understood as symptomatic of a terminal condition, in which farmers are replaced progressively by corporate ownership; or whether family farms will persist as a social formation, albeit increasingly subsumed by off-farm interests. Using evidence from the Australian processing tomato sector, this article documents the changing social and economic formation of ‘family farming’. We argue that in this industry, the appropriate way to describe farmers is through the deployment of that a new category of farming; farm family entrepreneurs. This phrase is coined to describe the situation where family units remain at the social and economic heart of farm ownership and operation, but in the context where they relate to their land-based assets through legal and financial structures characteristic of the wider economy. As this article explores, this formation seems to represent an accommodating modus operandi for farm units within neo-liberal agricultural governance. Nevertheless, however, this duality of family-based structures and capitalist entrepreneurialism inevitably provokes a series of tensions, whose resolution requires a variety of organizational strategies to be put in place. 相似文献
39.
By the late 1990s, Pierre Bourdieu had become the primary public intellectual of major social scientific status at the head of the anti-globalization movement that emerged in France and in other Western European countries. This article discusses how Bourdieu became a leading public intellectual, a role that seems to contrast with his early years as a professional sociologist. It explores what seemed to change in Bourdieu’s activities and outlook as sociologist and what seems to have remained constant. It identifies several institutional conditions that seemed necessary for Bourdieu to be able to play the kind of public intellectual role he did in his later years. Bourdieu’s movement from a peripheral position to a central location in the French intellectual field, the changing character of the field itself, the growing influence of the mass media in French political and cultural life, the failures of the French Socialists in power, a cultural legacy of leading critical intellectuals in France, a unifying national issue of globalization, and the political conjuncture in 1995 all intersected in ways that opened a path for Bourdieu to choose new and more frequent forms of political action. His responses to that combination of factors at different moments reveal both a striking continuity in desire to preserve the autonomy of intellectual life and a change in view and strategy on how best to do that. The article concludes with a brief evaluation of Bourdieu’s public intellectual role. 相似文献
40.
Objective. The risk compensation hypothesis suggests that drivers enjoying greater safety will drive more recklessly and thereby impose greater risks on nonoccupants. We provide a test of the risk compensation hypothesis in the context of state seatbelt laws and belt use rates. Methods. Fixed‐effects models with policy and demographic variables are estimated using annual state data from 1985 to 2002 to test the effect of seatbelt laws and seatbelt use rates on logged fatality rates for occupants, pedestrians, motorcyclists, and all nonoccupants in separate models. Results. Contrary to the risk compensation hypothesis, the results indicate that both occupants and nonoccupants enjoy greater safety due to state mandatory use laws and increased safety belt use rates. Conclusion. Overall, seatbelt laws and the higher belt use these laws induce do not increase nonoccupant risk exposure. If anything, these laws and the accompanying increase in belt use result in safer driving behavior. 相似文献