Current Status Data

Decision-making is one of the vital roles of competent technical skills that helps in the effective functioning of business management. The development in business strategy has made a way to develop the technical and non-technical skills of both managers and employees. The analysis of the technical and non-technical skills of the manager is essential in the growth of business management. This article aims to analyze the competent technical skills of the managers those aid in taking efficient decisions. The analyzed competent skills of managers included technical skills, listening skills, documentation, external support in solving the issues, standard decision, lesson learned, and correct decisions. The data was collected through an online survey from 90 respondents and analyzed in SPSS using frequency analysis and factor analysis. The study finds that the manager's competent and technical skill is vital in the decision-making process. The study identified the nine most influential factors that contribute to a manager's competent and technical skills. Further, the compliance and non-compliance rate on identified factors were explored and interesting results were obtained. The effectiveness of these skills leads to a successful organization.

Decision-making is one of the vital roles of competent technical skills that helps in the effective functioning of business management. The development in business strategy has made a way to develop the technical and non-technical skills of both managers and employees. The analysis of the technical and non-technical skills of the manager is essential in the growth of business management. This article aims to analyze the competent technical skills of the managers those aid in taking efficient decisions. The analyzed competent skills of managers included technical skills, listening skills, documentation, external support in solving the issues, standard decision, lesson learned, and correct decisions. The data was collected through an online survey from 90 respondents and analyzed in SPSS using frequency analysis and factor analysis. The study finds that the manager's competent and technical skill is vital in the decision-making process. The study identified the nine most influential factors that contribute to a manager’s competent and technical skills. Further, the compliance and non-compliance rate on identified factors were explored and interesting results were obtained. The effectiveness of these skills leads to a successful organization.

This article extends the scope of empirical likelihood methodology in three directions: to allow for plug-in estimates of nuisance parameters in estimating equations, slower than √ n-rates of convergence, and settings in which there are a relatively large number of estimating equations compared to the sample size. Calibrating empirical likelihood confidence regions with plug-in is sometimes intractable due to the complexity of the asymptotics, so we introduce a bootstrap approximation that can be used in such situations. We provide a range of examples from survival analysis and nonparametric statistics to illustrate the main results.

Estimation for the Birnbaum-Saunders (BS) regression model has been discussed by various authors when data are either complete or subject to Type-I or random censoring. But, this problem has not been considered for the case of interval censoring. In this article, we discuss the estimation of a regression model with current status data when the failure times follow the BS distribution. We estimate the parameters by the method of maximum likelihood, and derive the asymptotic distribution of these estimators. The performance of these estimators is then assessed through Monte Carlo simulations for different sample sizes under two types of monitoring. Finally, an analysis of real data is used to illustrate the proposed method.

The white–bellied spider monkey, Ateles belzebuth, is one of the seven species that inhabits both lowland and montane forests in the Peruvian Amazon. The lowland populations are locally extinct over a large part of the species range there, but there is very little information on the montane forest populations other than records of some groups in a few localities. The lack of information motivated us to conduct this study to determine the current status of these spider monkeys and identify the threats to their populations. Transect censuses were carried out in November 2016, February 2017 and May–July 2017. In 786 km of tran-sects walked, we observed 44 groups of five primate species, the most common being A. belzebuth and Cebus yuracus (both with 13 groups). Most of the A. belzebuth groups were observed in Las Hamacas (six groups) and La Meseta (four groups) belonging to the Área de Conservación Privada Los Chilchos. Of the four species for which we obtained complete group counts, the largest groups were those of A. belzebuth (average 16 ± 6.1, n = 5) and the smallest of Alouatta seniculus (average 4.8 ± 1.2). The highest relative abundance was for A. belzebuth (2.56 individuals/10 km) and lowest for A. seniculus (0.53 individuals/10 km). South of the Río Marañón, the distribution of A. belzebuth is restricted to the montane forests of the regions of Amazonas, San Martín, La Libertad, and part of Huánuco to the Río Monzón, but it is locally extinct between the ríos Tocache and Monzón. Logging, hunting and deforestation for agriculture and cattle ranching were found to be the main threats to the survival of A. belzebuth and other primates in the areas we surveyed.

This study concerns particularly Draa Naga arboretum, created inside the forest station of Djbel El Ouahch (Constantine, east-Algeria) in the fifties. It is occupies an area of 31 hectares and is actually managed by the Forest Conservation, it is a valuable tool for education and ecotourism. Until know, no system of measurement or supervision of its viability was created so that the ecological status is unknown at all. Analyses results show a mid viability of the arboretum which is indicated by a medium stability of forests stand's quality, a high rate of mortality and a very low future potentiality (0% of regeneration). In addition to that, artificial forest suffers from invasion of autochthones species, the principal pressure affecting the arboretum which is placed among forest. Consideration of two dendrologous types of forest's stand reveals that broadleaved trees ones presents better attribute than conifers. The necessity of a management plan is evident to ameliorate the place and so is a regular survey. For that, a forest management plan is proposed for the arboretum.

We study a binary regression model where the response variable ¢ is the indicator of an event of interest (for example, the incidence of cancer) and the set of covariates can be partitioned as (X;Z) where Z (real valued) is the covariate of primary interest and X (vector valued) denotes a set of control variables. For any fixed X, the

There is no information on the primate communities of the montane forests of the Peruvian Amazon except in the northeast. The regions of Pasco and Ucayali have never been explored for the primates that occur there, which motivated us to conduct this study, to assess the conservation status of the primates and especially to determine the limits of the distribution of the Peruvian yellow-tailed woolly monkey (Lagothrix flavicauda). Linear transect censuses were conducted from July to October 2018 in six survey sites. In 709 km traveled, we saw 28 groups of five species. The Peruvian woolly monkey (Lagothrix lagoth-richa tschudii) and the Marañón white-fronted capuchin (Cebus yuracus) were the most sighted, with eight and seven groups, respectively. Lagothrix flavicauda was not recorded in any of the survey sites, but we do not rule out its presence in other areas, particularly in Pasco. Red howler monkey (Alouatta seniculus) groups averaged 3.4 members, ranging from 2 to 6. The black spider monkey (Ateles chamek) and C. yuracus were seen in larger groups. The largest of three groups of the Andean saddle-back tamarin (Leontocebus leucogenys), seen in two localities, was seven. Relative abundance was higher for the species sighted in Ucayali, the highest being A. chamek with 1.5 groups/10 km. In Huánuco, the geographic distribution of L. flavicauda ranges as far as the montane forest of the province of Pachitea to the southeast, between 1,900 and 2,800 m above sea level. The geographic distribution of L. l. tschudii on the other hand extends to the western side of the Ucayali, to the ríos Pachitea and Pichis, and includes the montane forests of Pasco, Ucayali and part of Huánuco. Deforestation and hunting are the main threats to the survival of primates and other wildlife, particularly in Pasco and Huánuco.

This paper discusses the analysis of interval-censored failure time data, which has recently attracted a great amount of attention (Li and Pu, Lifetime Data Anal 9:57-70, 2003; Sun, The statistical analysis of interval-censored data, 2006; Tian and Cai, Biometrika 93(2):329-342, 2006; Zhang et al., Can J Stat 33:61-70, 2005). Interval-censored data mean that the survival time of interest is observed only to belong to an interval and they occur in many fields including clinical trials, demographical studies, medical follow-up studies, public health studies and tumorgenicity experiments. A major difficulty with the analysis of interval-censored data is that one has to deal with a censoring mechanism that involves two related variables. For the inference, we present a transformation approach that transforms general interval-censored data into current status data, for which one only needs to deal with one censoring variable and the inference is thus much easy. We apply this general idea to regression analysis of interval-censored data using the additive hazards model and numerical studies indicate that the method performs well for practical situations. An illustrative example is provided.

The nonparametric maximum likelihood estimator for current-status data has been known for at least 40 years, but only recently have the mathematical-statistical properties been clarified. This note provides a case study in the important and often studied context of estimating age-specific immunization intensities from a seroprevalence survey. Fully parametric and spline-based alternatives (also based on continuous-time models) are given. The basic reproduction number Ro exemplifies estimation of a functional. The limitations implied by the necessarily rather restrictive epidemiological assumptions are briefly discussed.

In biostatistics applications interest often focuses on the estimation of the distribution of a timevariable T. If one only observes whether or not T exceeds an observed monitoring time C, then the data structure is called current status data, also known as interval censored data, case I. We consider this data structure extended to allow the presence of both time-independent covariates and time-dependent covariate processes that are observed until the monitoring time. We assume that the monitoring process satisfies coarsening at random.

For bivariate current status data with univariate monitoring times, the identifiable part of the joint distribution is three univariate cumulative distribution functions, namely the two marginal distributions and the bivariate cumulative distribution function evaluated on the diagonal. We show that smooth functionals of these univariate cumulative distribution functions can be efficiently estimated with easily computed nonparametric maximum likelihood estimators based

We study nonparametric estimation for current status data with competing risks. Our main interest is in the nonparametric maximum likelihood estimator (MLE), and for comparison we also consider a simpler 'naive estimator'. Groeneboom, Maathuis and Wellner proved that both types of estimators converge globally and locally at rate n 1/3 . We use these results to derive the local limiting distributions of the estimators. The limiting distribution of the naive estimator is given by the slopes of the convex minorants of correlated Brownian motion processes with parabolic drifts. The limiting distribution of the MLE involves a new self-induced limiting process.

We study nonparametric estimation of the sub-distribution functions for current status data with competing risks. Our main interest is in the nonparametric maximum likelihood estimator (MLE), and for comparison we also consider a simpler "naive estimator." Both types of estimators were studied by Jewell, van der Laan and Henneman [Biometrika (2003) 90 183-197], but little was known about their large sample properties. We have started to fill this gap, by proving that the estimators are consistent and converge globally and locally at rate n 1/3 . We also show that this local rate of convergence is optimal in a minimax sense. The proof of the local rate of convergence of the MLE uses new methods, and relies on a rate result for the sum of the MLEs of the sub-distribution functions which holds uniformly on a fixed neighborhood of a point. Our results are used in Groeneboom, Maathuis and Wellner [Ann. Statist. (2008) 36 1064-1089] to obtain the local limiting distributions of the estimators. . This reprint differs from the original in pagination and typographic detail. 1 2 P. GROENEBOOM, M. H. MAATHUIS AND J. A. WELLNER

Background: Chronic hepatitis C virus infection is prevalent and often causes hepatic fibrosis, which can progress to cirrhosis and cause liver cancer or liver failure. Study of fibrosis progression often relies on imputing the time of infection, often as the reported age of first injection drug use. We sought to examine the accuracy of such imputation and implications for modeling factors that influence progression rates.

The pool adjacent violator algorithm has long been known to give the maximum likelihood estimator of a series of ordered binomial parameters, based on an independent observation from each distribution (see . This result has immediate application to estimation of a survival distribution based on current survival status at a set of monitoring times. This paper considers an extended problem of maximum likelihood estimation of a series of 'ordered' multinomial parameters p i = ( p 1i , p 2i , . . . , p mi ) for 1 i k, where ordered means that p j1 p j2 · · · p jk for each j with 1 j m − 1. The data consist of k independent observations X 1 , . . . , X k where X i has a multinomial distribution with probability parameter p i and known index n i 1. By making use of variants of the pool adjacent violator algorithm, we obtain a simple algorithm to compute the maximum likelihood estimator of p 1 , . . . , p k , and demonstrate its convergence. The results are applied to nonparametric maximum likelihood estimation of the sub-distribution functions associated with a survival time random variable with competing risks when only current status data are available .

Summary.  The relative frailty variance among survivors provides a readily interpretable measure of how the heterogeneity of a population, as represented by a frailty model, evolves over time. We discuss the properties of the relative frailty variance, show that it characterizes frailty distributions and that, suitably rescaled, it may be used to compare patterns of dependence across models and data sets. In shared frailty models, the relative frailty variance is closely related to the cross-ratio function, which is estimable from bivariate survival data. We investigate the possible shapes of the relative frailty variance function for the purpose of model selection, and we review available frailty distribution families in this context. We introduce several new families with contrasting properties, including simple but flexible time varying frailty models. The benefits of the approach that we propose are illustrated with two applications to bivariate current status data obtained from serological surveys.