Conditional tests in a competing risks model

Testing for equality of competing risks based on their cumulative incidence functions (CIFs) or their cause specific hazard rates (CSHRs) has been considered by many authors. The finite sample distributions of the existing test statistics are in general complicated and the use of their asymptotic distributions can lead to conservative tests. In this paper we show how to perform some of these tests using the conditional distributions of their corresponding test statistics instead (conditional on the observed data). The resulting conditional tests are initially developed for the case of k = 2 and are then extended to k > 2 by performing a sequence of two sample tests and by combining several risks into one. A simulation study to compare the powers of several tests based on their conditional and asymptotic distributions shows that using conditional tests leads to a gain in power. A real life example is also discussed to show how to implement such conditional tests.     

Does self-employment contribute to national happiness?

Recent studies showed that self-employment impacts individual happiness either positively or negatively. Rather than considering the happiness effects at the individual level, we assess whether self-employment effects spread and impact the domestic happiness beyond the involved individuals. We distinguish a direct effect of self-employment on life satisfaction and an indirect effect through the impact of self-employment on per capita income and the subsequent impact of income on life satisfaction. Using panel data analysis for 15 OECD countries over a period of 18 years, we investigate empirically whether countries with higher levels of self-employment are happier, by disentangling the two previously mentioned effects. We remedy the potential endogeneity problem when estimating the indirect effect by instrumenting the self-employment rate. The main finding is a significant and negative direct effect which is larger in magnitude than the indirect effect, resulting in an overall negative effect of self-employment on the domestic happiness.     

On the contribution of sectoral natural population growth to the aggregate poverty change

This note extends the Ravallion and Huppi (World Bank Econ Rev 5(1):57–82, 1991) aggregate poverty change decomposition to account for the distinct contribution of migration and differential natural population growth between sectors to the aggregate poverty change. We apply our decomposition to three Least Developing countries. We find that accounting for sectoral difference in natural population growth has a considerable impact on national poverty change. Responsible editor: Alessandro Cigno     

Nonhomogeneous poisson processes as overhaul models

Hollander and Proschan (1974) studied nonhomogeneous Poisson processes as models for systems subject to overhauls. They did not postulate a functional form for the intensity, but showed that certain basic assumptions about the deterioration of the system implied that the mean function is superadditive. They studied tests of the null hypothesis that the intensity is constant with the alternative restricted to superadditive mean functions. For estimation purposes, the class of superadditive mean functions is too broad. We assume that the intensity is nondecreasing between overhauls and that at an overhaul it does not fall below its average prior to the overhaul. These two assumptions imply that the mean function is star-shaped. We obtain the restricted maximum-likelihood estimates under these two assumptions and under the star-shaped restriction. The two estimates are compared on a data set.     

A Non‐parametric ANOVA‐type Test for Regression Curves Based on Characteristic Functions

This article studies a new procedure to test for the equality of k regression curves in a fully non‐parametric context. The test is based on the comparison of empirical estimators of the characteristic functions of the regression residuals in each population. The asymptotic behaviour of the test statistic is studied in detail. It is shown that under the null hypothesis, the distribution of the test statistic converges to a finite combination of independent chi‐squared random variables with one degree of freedom. The coefficients in this linear combination can be consistently estimated. The proposed test is able to detect contiguous alternatives converging to the null at the rate n ^{? 1 ∕ 2}. The practical performance of the test based on the asymptotic null distribution is investigated by means of simulations.     

Guided Censored Regression

Parametrically guided non‐parametric regression is an appealing method that can reduce the bias of a non‐parametric regression function estimator without increasing the variance. In this paper, we adapt this method to the censored data case using an unbiased transformation of the data and a local linear fit. The asymptotic properties of the proposed estimator are established, and its performance is evaluated via finite sample simulations.     

Two-Term Edgeworth Expansions for the Classes of U- and V-statistics

Much effort has been devoted to deriving Edgeworth expansions for various classes of statistics that are asymptotically normally distributed, with derivations tailored to the individual structure of each class. Expansions with smaller error rates are needed for more accurate statistical inference. Two such Edgeworth expansions are derived analytically in this paper. One is a two-term expansion for the standardized U-statistic of order m, m ? 3, with an error rate o(n^{? 1}). The other is an expansion with the same error rate for the distribution of the standardized V-statistic of the same order. In deriving the Edgeworth expansion, we made use of the close connection between the V- and U-statistics, which permits to first derive the needed expansion for the related U-statistic, then extend it to the V-statistic, taking into consideration the estimation of all difference terms between the two statistics.     

Authenticity and community process

How does community process constitute an opening to an authentic existence? Martin Heidegger suggests that authentic Being-in-the-world is rooted in self-reflection and isolation from others—far from the public realm. Conversely, Mary Parker Follett argues that collaborative processes embed action with meaning that have far-reaching implications for individual development as well as for democracy. Drawing on classical political philosophy’s public space and citizenship, this research maintains that community process enhances authentic, self-aware participatory practices—fundamental for one’s full development and practical democracy. Public and nonprofit administrators working in community-based or oriented organizations ought to cultivate opportunities for such development.     

Clan information market games

We introduce a TU-game that describes a market where information is distributed among several agents and all these pieces of information are necessary to produce a good. This situation will be called clan information market. The class of the corresponding TU-games, the clan information market games (CIGs), is a subset of the class of clan games. We provide some well-known point solutions for CIGs in terms of the market data.