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排序方式: 共有352条查询结果,搜索用时 15 毫秒
1.
In studies with recurrent event endpoints, misspecified assumptions of event rates or dispersion can lead to underpowered trials or overexposure of patients. Specification of overdispersion is often a particular problem as it is usually not reported in clinical trial publications. Changing event rates over the years have been described for some diseases, adding to the uncertainty in planning. To mitigate the risks of inadequate sample sizes, internal pilot study designs have been proposed with a preference for blinded sample size reestimation procedures, as they generally do not affect the type I error rate and maintain trial integrity. Blinded sample size reestimation procedures are available for trials with recurrent events as endpoints. However, the variance in the reestimated sample size can be considerable in particular with early sample size reviews. Motivated by a randomized controlled trial in paediatric multiple sclerosis, a rare neurological condition in children, we apply the concept of blinded continuous monitoring of information, which is known to reduce the variance in the resulting sample size. Assuming negative binomial distributions for the counts of recurrent relapses, we derive information criteria and propose blinded continuous monitoring procedures. The operating characteristics of these are assessed in Monte Carlo trial simulations demonstrating favourable properties with regard to type I error rate, power, and stopping time, ie, sample size. 相似文献
2.
Oliveira Flávio G. Tapisso Joaquim T. von Merten Sophie Rychlik Leszek Fonseca Paulo J. Mathias Maria da Luz 《Urban Ecosystems》2021,24(5):851-862
Urban Ecosystems - The development of urban areas imposes challenges that wildlife must adapt to in order to persist in these new habitats. One of the greatest changes brought by urbanization has... 相似文献
3.
Dieter Weiss 《Social indicators research》1992,26(4):367-389
The paper gives an assessment of the theoretical foundations of development planning laid in the 1950s and 1960s, and the conceptual shifts since the turbulent 1970s questioning previous patterns of macroeconomic regulation. The call today is for management styles suited to cope with evolutionary processes. Their crucial elements in the face of overall change are sensitive early diagnosis, flexible adjustment, continuous individual and social learning, the building of technological potential, and self-organization. There is an emerging search for an evolutionary ethics accepting responsibility for the further continuation of life on the planet in view of ecological constraints and recognizing basic principles of evolution such as openness, non-equilibrium, and the positive role of fluctuations in reaching higher levels of complexity and order. Value systems have an ever more explicit impact on the direction of social change. 相似文献
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Laura Bernardi Andreas Klärner Holger von der Lippe 《Revue europeenne de demographie》2008,24(3):287-313
This article contributes to the ongoing debate on the economic determinants of fertility behavior by addressing the role of
job insecurity in couples’ intentions concerning parenthood and its timing. It starts from the hypothesis that cultural values
moderate individuals’ reactions to job insecurity and the way it is related to family formation. With a systematic thematic
content analysis of a set of semi-structured interviews with childless men and women around the age of 30 in eastern and western
Germany, we are able to show that there are substantial differences in the consequences of job insecurity on intentions to
have a first child. In western Germany, a relatively secure job career is expected to precede family formation, and this sequence
of transitions is rather rigid, whereas in eastern Germany job security and family formation are thought of and practiced
as parallel investments. We suggest that the lack of convergence in family formation patterns between eastern and western
Germany after the unification of the country in 1990 is partially related to different attitudes toward job insecurity in
the two contexts. 相似文献
8.
Wolfgang Bellaire M.D. Dieter Caspari M.D. 《Journal of gambling studies / co-sponsored by the National Council on Problem Gambling and Institute for the Study of Gambling and Commercial Gaming》1992,8(2):143-150
From 1980 to mid-1990 fifty-one gamblers were evaluated and treated at the psychiatric university hospital of Homburg/Saar in Germany. All were men with a mean age of 33.7 years. Gambling had lasted 5.2 years on average. Most patients were motivated to undergo therapy by members of their family. The majority of them had been in psychotherapeutic treatment before. Thirty-six of the 51 patients had committed punishable acts including fraud and embezzlement and, in 7 cases, robbery. The sample could be divided into three clinical subgroups. The first group consisted of patients with severe psychiatric diseases such as schizophrenia, manic-depressive illness or organic brain disorder. Patients of the second group suffered from serious personality disorders. Those of the third group showed deep-rooted problems in their current relationships.This article is an extension of the special issue on Gambling in Europe edited by Iver Hand, M.D. 相似文献
9.
Approximation of a density by another density is considered in the case of different dimensionalities of the distributions. The results have been derived by inverting expansions of characteristic functions with the help of matrix techniques. The approximations obtained are all functions of cumulant differences and derivatives of the approximating density. The multivariate Edgeworth expansion follows from the results as a special case. Furthermore, the density functions of the trace and eigenvalues of the sample covariance matrix are approximated by the multivariate normal density and a numerical example is given 相似文献
10.
Burge E Kuhne N Berchtold A Maupetit C von Gunten A 《European review of aging and physical activity》2012,9(1):27-39
The objectives of this study were to describe the different modalities of physical activity programs designed for moderate
to severe dementia and to identify their impact on functional independence in activities of daily living (ADL). A critical
review of randomized controlled trials related to the impact of physical activity programs in moderately to severely demented
persons on ADL performance and meta-analysis of the identified studies were performed. Among the 303 identified articles,
five responded to the selection criteria. Four out of the five studies demonstrated limited methodological quality. In one
high-quality study, physical activity programs significantly delayed deterioration of ADL performance. The program components
and ADL assessment tools vary widely across studies. Although the proposed treatments have not proven their efficiency in
improving the ADL status of the patients, they were able to limit the decline in ADL functioning. Future research is warranted
in order to identify clinically relevant modalities for physical activity programs for people with moderate to severe dementia. 相似文献