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11.
It is well-known that the nonparametric maximum likelihood estimator (NPMLE) of a survival function may severely underestimate the survival probabilities at very early times for left truncated data. This problem might be overcome by instead computing a smoothed nonparametric estimator (SNE) via the EMS algorithm. The close connection between the SNE and the maximum penalized likelihood estimator is also established. Extensive Monte Carlo simulations demonstrate the superior performance of the SNE over that of the NPMLE, in terms of either bias or variance, even for moderately large Samples. The methodology is illustrated with an application to the Massachusetts Health Care Panel Study dataset to estimate the probability of being functionally independent for non-poor male and female groups rcspectively. 相似文献
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The authors applied the stage-of-change construct in the transtheoretical model to examine the distribution of Asian (n = 869), African American (n = 373), White (n = 1322), and Hispanic (n = 535) American undergraduate students across the 5 stages of change for exercise. Stage of change varied as a function of ethnicity. Higher percentages of minorities were in the precontemplation and contemplation stages. The likelihood of being in these stages was from 43% to 82% greater for minorities than for White students. Also examined were the congruency between stage of change and self-reported levels of physical activity. Half of the sedentary students and 15.6% of the active students were misclassified by the stage-of-change procedure. Misclassification rates were higher for minority women (27.8%) than for White women (17.8%) and for Asian students (24.6%) compared with all others (20.6%). The results of this study have implications for the design of physical activity interventions based on stage of change. 相似文献
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Rick Welsh 《Rural sociology》1998,63(2):199-213
Abstract According to a number of observers of the U.S. economy, large publicly traded corporations can be viewed as a social problem primarily because of their association with the concentration of wealth and power. In agriculture, nine states have laws which restrict or proscribe public corporations from engaging in farming. Also, groups and individuals have attempted to preserve non-corporate production enterprises in agriculture through the establishment of direct markets such as farmers' markets. Proponents of such efforts believe public corporations have negative economic impacts; opponents of such efforts, especially efforts to establish and retain anti-corporate farming laws, argue that corporations can provide economic benefits to rural areas. These debates beg the question of whether ownership and direct marketing arrangements have important influences on economic outcomes such as levels of cash returns from farming and increases in the number of farms realizing cash gains. Using multi-year, county-level data from the Census of Agriculture, this study finds that, even when holding a number of important variables constant, ownership arrangements, as well as the (interaction between the percentage of total sales which are direct sales and the percentage of farms selling directly, are important determinants of both net cash returns and the percentage of farms realizing cash gains. 相似文献
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Control charts typically used to monitor process centrality and dispersion either assume normally distributed output or appeal to the viability of the central limit theorem. This appeal to the central limit theorem is frequently made on behalf of samples consisting of 10 or fewer items. Control charts for centrality and dispersion are presented for processes with inverse Gaussian distributed output. 相似文献
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Behavior analysts have offered accounts of the behavior involved in matching to sample and delayed matching to sample. But until recently have not offered a behavioral analysis of generalized matching-to-sample. The concept of joint control, however, seems especially suited to such an analysis The present study used a joint-control procedure to train five adult women to acquire a generalized sequencing behavior using an unfamiliar language. After joint-control training the participants were able to produce untrained picture sequences, and blocking the mediating response during the sequencing task resulted in a reduction in the number of accurate sequences. These results clearly support response mediation as a precurrent to various kinds of complex human behavior. 相似文献
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Abstract Following a rise in university-industry relationships (UIRs), scholars began questioning the efficacy of those relationships, as well as whether industry and university research interests and integrity are being compromised. Although many of these studies focus on the university, few examine the perspectives of industry participants. We conducted intensive interviews with 63 managers and scientists at agricultural biotechnology companies involved in UIRs related to agricultural biotechnology. Our analysis of their comments reveals nuanced critical perspectives of UIRs and creative ideas for reforming policies and practices. Industry representatives listed many advantages of UIRs, but some also expressed an interest in reforming policies to preserve a public-interest emphasis for university research. We conclude by considering the structural relationships that may explain the industry representatives' critical evaluations and by identifying policy implications. 相似文献
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