Correction to: The Impact of Agricultural Technologies on Poverty and Vulnerability of Smallholders in Ethiopia: A Panel Data Analysis

Social Indicators Research - The article The Impact of Agricultural Technologies on Poverty and Vulnerability of Smallholders in Ethiopia: A Panel Data Analysis, written by Wubneshe Dessalegn Biru,...     

Restricted tests for testing independence of time to failure and cause of failure in a competing-risks model

We consider the competing-risks problem without making any assumption concerning the independence of the risks. Maximum-likelihood estimates of the cause-specific hazard rates are obtained under the condition that their ratio is monotone. We also consider the likelihood-ratio test for testing the proportionality of two cause-specific hazard rates against the alternative that the ratio of these two hazard rates is monotonic. This testing problem is equivalent to testing independence against likelihood-ratio dependence of the time to failure and the cause of failure in the competing-risks setup. We allow for random censoring on the right. The asymptotic null distribution of the test statistic is obtained and is found to be of the chi-bar-square type. The problem is extended to the case of more than two risks. A numerical example is given to illustrate the procedure.     

Marriage and Subjective Well-Being: How and Why Context Matters

Over the last 20 years the academic community has experienced a burgeoning interest in the causes and correlates of subjective well-being. One of the most consistent findings has been that married respondents report higher levels of happiness and life satisfaction than unmarried respondents. Despite its prevalence, scant empirical research has focused on the potential mechanisms driving this relationship. The current work draws on the Behavior Risk Factor Surveillance System along with 2000 US Census data to investigate the role of context and reference groups in shaping the relationship between marriage and well-being. The primary research question is whether marriage has a greater influence on life satisfaction when it is more common and thus more normative? The findings offer new insight into the marriage/well-being relationship and have broad implication for how we think about the study of the causes and correlates of subjective well-being.     

Enabling high-dimensional range queries using <Emphasis Type="Italic">k</Emphasis>NN indexing techniques: approaches and empirical results

Many modern search applications are high-dimensional and depend on efficient orthogonal range queries. These applications span web-based and scientific needs as well as uses for data mining. Although k-nearest neighbor queries are becoming increasingly common due to mobile and geospatial applications, orthogonal range queries in high-dimensional data remain extremely important and relevant. For efficient querying, data is typically stored in an index optimized for either kNN or range queries. This can be problematic when data is optimized for kNN retrieval and a user needs a range query or vice versa. Here, we address the issue of using a kNN-based index for range queries, as well as outline the general computational geometry problem of adapting these systems to range queries. We refer to these methods as space-based decompositions and provide a straightforward heuristic for this problem. Using iDistance as our applied kNN indexing technique, we also develop an optimal (data-based) algorithm designed specifically for its indexing scheme. We compare this method to the suggested naïve approach using real world datasets. The data-based algorithm consistently performs better.     

Viability of Auction‐Based Revenue Management in Sequential Markets

The Internet is providing an opportunity to revenue management practitioners to exploit the potential of auctions as a new price distribution channel. We develop a stochastic model for a high‐level abstraction of a revenue management system (RMS) that allows us to understand the potential of incorporating auctions in revenue management in the presence of forecast errors associated with key parameters. Our abstraction is for an environment where two market segments book in sequence and revenue management approaches consider auctions in none, one, or both segments. Key insights from our robust results are (i) limited auctions are best employed closest to the final sale date, (ii) counterbalancing forecast errors associated with overall traffic intensity and the proportion of customer arrivals in a segment is more important if an auction is adopted in that segment, and (iii) it is critically important not to err on the side of overestimating market willingness to pay.     

Is There a Place for Virtual Poverty Funds in Pro‐Poor Public Spending Reform? Lessons from Uganda's PAF

Various developing countries with weak public expenditure management systems are establishing virtual poverty funds (VPFs), drawing on the experience of Uganda's Poverty Action Fund. As a mechanism for tagging and tracking the performance of specific poverty‐reducing expenditures in the budget, a VPF can be useful. However, this article argues that such devices should be treated from the outset as transitional, and as part of wider processes of strengthening public expenditure management; otherwise, they can seriously distort public expenditure allocations and management systems, potentially undermining growth. Emphasis needs to be placed on identifying the right balance of expenditures in the entire budget; improving the effectiveness and efficiency of existing allocations; and developing better public‐sector policies for promoting pro‐poor private sector growth.     

Child protection: a new approach in South Australia

This paper argues the case for an integrated approach to child protection services, embracing children's safety, risk and needs and incorporating formal assessment instruments. It then provides a brief overview of the new child protection system in South Australia. The steady rise in child abuse/neglect reports raises questions about how best to provide child protection services. Analysis of South Australian data suggests that much of the rise can be attributed to an increase in reports of neglect and emotional abuse and an increase in re‐notifications. This in turn raises questions about the traditional investigative approach. In 1995 Messages from Research advocated that agencies re‐focus on children's needs and concentrate less on investigations into safety and risk. The critical question is how to distinguish families requiring investigation from those needing support. The latest research suggests that such decision‐making in child protection is generally inconsistent and unreliable. This paper argues that statutory agencies should use formal assessment tools to determine the level and nature of their interventions. These arguments have been critical in the development of the new child protection model in SA, which relies on a centralized intake, differential response to reports and the structured decision‐making system. Initial evaluation of the new model indicates improvements in consistency of initial screening and responses to children in danger. Copyright © 1999 John Wiley & Sons, Ltd.     

Blinded sample size recalculation for clinical trials with normal data and baseline adjusted analysis

Baseline adjusted analyses are commonly encountered in practice, and regulatory guidelines endorse this practice. Sample size calculations for this kind of analyses require knowledge of the magnitude of nuisance parameters that are usually not given when the results of clinical trials are reported in the literature. It is therefore quite natural to start with a preliminary calculated sample size based on the sparse information available in the planning phase and to re‐estimate the value of the nuisance parameters (and with it the sample size) when a portion of the planned number of patients have completed the study. We investigate the characteristics of this internal pilot study design when an analysis of covariance with normally distributed outcome and one random covariate is applied. For this purpose we first assess the accuracy of four approximate sample size formulae within the fixed sample size design. Then the performance of the recalculation procedure with respect to its actual Type I error rate and power characteristics is examined. The results of simulation studies show that this approach has favorable properties with respect to the Type I error rate and power. Together with its simplicity, these features should make it attractive for practical application. Copyright © 2009 John Wiley & Sons, Ltd.