Estimation and prediction for a Burr type-III distribution with progressive censoring

We consider estimation of unknown parameters and reliability characteristics of a Burr type-III distribution under progressive censoring. Predictive estimates for censored observations and the associated prediction intervals are also obtained. We derive maximum-likelihood estimators of unknown quantities using the EM algorithm and then also obtain the observed Fisher information matrix. We provide various Bayes estimators for unknown parameters under the squared error loss function. Highest posterior density and asymptotic intervals are also constructed. We evaluate performance of proposed methods using simulations. Finally, an illustrative example is presented in support of the methods discussed.     

Exercise or physical activity and cognitive function in adults with type 2 diabetes,insulin resistance or impaired glucose tolerance: a systematic review

Background

Diabetes is an important risk factor for cognitive impairment. Although some studies suggest that physical exercise can minimize age-related cognitive declines or improve brain morphology or function, benefits in diabetes or impaired glucose tolerance are unclear. Therefore, our aim was to evaluate the efficacy of exercise or physical activity on cognition in adults with type 2 diabetes, insulin resistance or impaired glucose tolerance.

Methods

An electronic search for studies published from the earliest record until February 2017 was conducted using Medline, EMBASE, SPORTDiscus, CINAHL, and PsycINFO. Any experimental or observational study designs were included, as long as they were conducted in individuals of any age with type 2 diabetes, insulin resistance or impaired glucose tolerance, and they directly examined exercise/physical activity effects on cognitive outcomes or the relationship between changes in cognition and changes in either insulin resistance and glucose homeostasis. Study quality was assessed using the PEDro scale; data on participant and intervention characteristics and outcomes were extracted.

Results

Six studies enrolling 2289 participants met the eligibility criteria. Quality was modest and effect sizes variable and mostly small or negligible. Overall, four of the six studies (67%) reported significant benefits of greater exercise/physical activity participation for some aspects of cognition, but only 26% of cognitive outcomes were significant across all trials. Clinical improvements in insulin resistance/glucose homeostasis were related to improvements in cognitive function in three studies. Overall results were inconsistent, with benefits varying across exercise types and cognitive domains.

Conclusions

Literature does not provide evidence that physical activity or exercise interventions contribute to a better cognitive function in patients with type 2 diabetes or impaired glucose tolerance. Large-scale, long-term, robust randomized controlled trials are required to determine if exercise improves cognition in this high-risk cohort, and to investigate putative mechanistic links between cognition, body composition, metabolism, and inflammation in diabetes and related metabolic syndromes.

     

Corporate Governance and Tobin's Q as a Measure of Organizational Performance

This empirical study examines the relationship between corporate governance and organizational performance (OP), measured using Tobin's Q (TQ) in the context of an emerging economy for which, as yet, only a handful of studies have been conducted. We employ a system generalized method of moments approach controlling for endogeneity and test it on a newly created dataset comprising 324 listed firms in Pakistan. We find that board size, number of board committees and ownership concentration are positively linked with high TQ ratio, whilst board independence and CEO duality display a negative relationship. In terms of moderating effects, we find that ownership concentration negatively moderates the relationship between board independence and OP, as well as that of CEO duality and OP. The relationship between the number of board committees and OP is positively moderated by ownership concentration. Our findings contribute towards a better articulation and application of a more concrete measure of OP ? that of the TQ ratio ? whilst, at the same time, testing the board composition–performance relationship in the context of an upcoming and increasingly important emerging market. Wider applicability of results and policy implications are discussed.     

Intimate partner violence during pregnancy and use of antenatal care among rural women in southern Terai of Nepal

Background

Underutilisation of antenatal care services due to intimate partner violence during pregnancy has been well documented elsewhere, but it is understudied in Nepal. Our study aimed at exploring the impact of intimate partner violence on antenatal care service utilisation in southern Terai of Nepal.

Benefits of Surgical Smoothing and Spare Capacity: An Econometric Analysis of Patient Flow

In this study, we examine the hospital's ability to admit patients from its emergency department. From a medical perspective, the number of patients being admitted should depend solely on the patients’ clinical conditions. Using a large‐scale econometric study that includes detailed operational and clinical data on all cardiac patient encounters from a set of 128 hospitals over a period of four years, we show that this is not the case. In particular, we find that independent of their medical condition, many emergency patients are denied hospital admission because of a lack of inpatient beds. Our analysis suggests that having one more inpatient bed at the start of a day can increase the likelihood of an emergency room patient admission by around 3% on average. We examine two policies – active discharge and demand smoothing – that can help hospitals improve patient access. We find that some hospitals actively discharge inpatients when beds become scarce; hospitals that follow such an active discharge protocol are, on average, able to admit more patients. We also investigate to what extent the hospital's ability to smooth its surgical schedule impacts hospital admissions. Hospitals tend to schedule their elective patients early in the week (Mondays and Tuesdays), and discharge them by the weekend in order to minimize weekend staffing, effectively maximizing bed occupancy during the middle of the week. This “weekend effect” artificially induces variability, and reduces effective system capacity. We find that by scheduling patients more uniformly over the week, hospitals can dramatically increase patient access, obviating the need for active discharges or additional capacity investment. Our analysis quantifies these effects, and can help hospitals make effective capacity management decisions in order to improve patient flow.     

Estimating Abortion Incidence: Assessment of a Widely Used Indirect Method

Population Research and Policy Review - Induced abortion is a reproductive behavior that remains difficult to measure in countries where the procedure is highly restricted by law. Additionally, in...     

Optimal allocation of subjects in a matched pair cluster-randomized trial with fixed number of heterogeneous clusters

In cluster-randomized trials, investigators randomize clusters of individuals such as households, medical practices, schools or classrooms despite the unit of interest are the individuals. It results in the loss of efficiency in terms of the estimation of the unknown parameters as well as the power of the test for testing the treatment effects. To recoup this efficiency loss, some studies pair similar clusters and randomize treatment within pairs. However, the clusters within a treatment arm might be heterogeneous in nature. In this article, we propose a locally optimal design that accounts the clusters heterogeneity and optimally allocates the subjects within each cluster. To address the dependency of design on the unknown parameters, we also discuss Bayesian optimal designs. Performances of proposed designs are investigated numerically through some data examples.     

A REGRESSION APPROACH TO THE ESTIMATION OF THE FINITE POPULATION MEAN IN THE PRESENCE OF NON‐RESPONSE

This paper presents various estimators for estimating the population mean of the study variable y using information on the auxiliary variable x in the presence of non‐response. Properties of the suggested estimators are studied and compared with those of existing estimators. It is shown that the estimators suggested in this paper are among the best of all the estimators considered. An empirical study is carried out to demonstrate the performance of the suggested estimators and of others, and it is found that the empirical results support the theoretical study.     

Iso‐chi‐squared testing of 2 × k: ordered tables

The Pearson chi‐squared statistic for testing the equality of two multinomial populations when the categories are nominal is much less appropriate for ordinal categories. Test statistics typically used in this context are based on scorings of the ordinal levels, but the results of these tests are highly dependent on the choice of scores. The authors propose a test which naturally modifies the Pearson chi‐squared statistic to incorporate the ordinal information. The proposed test statistic does not depend on the scores and under the null hypothesis of equality of populations, it is asymptotically equivalent to the likelihood ratio test against the alternative of two‐sided likelihood ratio ordering.     

Policy Simulation of the Indian Silk Industry through an Econometric Model

This study aimed at understanding and quantifying the relationship between the important variables of the various subsectors of the Indian silk industry through an econometric simulation model, and using the model for forecasting as well as policy simulations. Forecasts of the endogenous variables of the system (demand, supply, and prices of mulberry cocoons, raw silk, and silk fabric) for the period 1991–92 to 2000–01 indicates that the growth in the industry will slow down in the future. Policy simulations were undertaken to assess the changes in the import price of raw silk, export price of fabrics, and regulation of the quantity of imports of raw silk on the silk industry. While imports and exports were closely linked, their impact on the silk industry was not very high. It was also revealed that the income of the consumers and mulberry acreage have significant influence on the industry.