An approximation of logarithmic functions in the regression setting

We consider a method of moments approach for dealing with censoring at zero for data expressed in levels when researchers would like to take logarithms. A Box–Cox transformation is employed. We explore this approach in the context of linear regression where both dependent and independent variables are censored. We contrast this method to two others, (1) dropping records of data containing censored values and (2) assuming normality for censored observations and the residuals in the model. Across the methods considered, where researchers are interested primarily in the slope parameter, estimation bias is consistently reduced using the method of moments approach.     

Correlates of honor ratings in a clinical clerkship employing a faculty forum evaluation system

5he purpose of this study was to determine whether or not suspected variables affected a surgery clerk's chances of being awarded an honor rating. Findings indicated a significant relationship between a student receiving an honor rating and his or her preceptor's predetermined level of student advocacy, the number of completed patient interview and physical examination write-ups, and final examination scores. There was no significant relationship found between honor ratings and the preceptor's status, the sequence in which the student was discussed or the length of time spent discussing the student at the final evaluation meeting, or the number of clinical faculty present at the meeting. These results lend support to the faculty forum evaluation approach, but suggest a need for further scrutiny of some influencing variables to ensure all students are fairly considered and honor ratings judiciously awarded.     

Evaluating a private foundation's health program

Public policy decisions in health are increasingly difficult and expensive. Although there will never be enough information available, private foundations can help to bridge the most important gaps in knowledge. Larger foundations may also wish to respond to those who doubt the value of foundation activities. This article reviews the experiences over the past eight years of The Robert Wood Johnson Foundation in employing evaluation and related social research procedures in the planning and implementation of a major philanthropic effort to improve the health and medical care of Americans. Discussed are the still evolving Foundation evaluation framework, the unanticipated problems in undertaking specific evaluations, and the substantive findings of some of the studies.     

Network analysis in evaluation: some words of caution

Network analysis, a methodology derived from general systems' theory, can be utilized as a community mental health administrative-evaluation procedure. Evaluation parameters derived from analysis of patient data as they “flow” through a network of agency services, provide measures of systemic functioning. These parameters include “longest paths” and various ratio relationships as evaluation measures of service delivery. The limitations of network analysis are examined by means of conceptual analyses, and phenomena that emerged from research experience. The necessity for both quantitative and qualitative data to ensure a meaningful evaluation of mental health services is explained. Conclusions about the value of the network analysis approach are considered.     

The validity of indices for rural health manpower needs assessment

Population-to-practitioner ratios have long been the primary index in the designation of health manpower shortage areas. This paper documents that application of the widely used population-to-dentist index results in understatement of the need for dental health manpower in rural areas. Through the analysis of utilization data collected from a statewide health screening program in Colorado, the practice of sole reliance on the population-to-dentist indices as an indicator of need was tested. Another measure, the area-(square miles) to-dentist ratio was formulated, examined, and found to be a more useful referent of the need for additional health manpower in rural areas. Utilization of dental services in sparsely settled rural counties of Colorado was unrelated to population-to-dentist ratios. A strong, statistically significant association of utilization with land area-to-dentist ratios was found. The findings of this analysis suggest a need for reevaluation of needs assessment methodologies used in the designation of health manpower shortage areas. Indices more sensitive to consumer circumstance than to the number of health care providers available must be considered.     

Improving TAIEX forecasting using fuzzy time series with Box–Cox power transformation

Box–Cox together with our newly proposed transformation were implemented in three different real world empirical problems to alleviate noisy and the volatility effect of them. Consequently, a new domain was constructed. Subsequently, universe of discourse for transformed data was established and an approach for calculating effective length of the intervals was then proposed. Considering the steps above, the initial forecasts were performed using frequently used fuzzy time series (FTS) methods on transformed data. Final forecasts were retrieved from initial forecasted values by proper inverse operation. Comparisons of the results demonstrate that the proposed method produced more accurate forecasts compared with existing FTS on original data.     

欧美农业补贴对世界农产品贸易的影响

欧美农业补贴政策对世界农产品贸易和世界其他主要农产品生产国的农业生产产生着巨大且多方面的影响。本文在分析欧盟和美国农业补贴的主要政策及特点的基础上,进一步分析欧美农业补贴政策对世界农产品贸易所产生的影响。欧美农业补贴政策加剧了国际农产品贸易摩擦,对发展中国家农业生产产生冲击,改变了贸易参与国的福利分配,因此欧美等发达国家应尽快削减直至取消农业补贴。     

A generalised Box–Cox transformation for the parametric estimation of clinical reference intervals

Parametric methods for the calculation of reference intervals in clinical studies often rely on the identification of a suitable transformation so that the transformed data can be assumed to be drawn from a Gaussian distribution. In this paper, the two-stage transformation recommended by the International Federation for Clinical Chemistry is compared with a novel generalised Box–Cox family of transformations. Investigation is also made of sample sizes needed to achieve certain criteria of reliability in the calculated reference interval. Simulations are used to show that the generalised Box–Cox family achieves a lower bias than the two-stage transformation. It was found that there is a possibility that the two-stage transformation will result in percentile estimates that cannot be back-transformed to obtain the required reference intervals, a difficulty not observed when using the generalised Box–Cox family introduced in this paper.