A bivariate mixture of negative binomial distributions and its applications

Abstract

We construct a new bivariate mixture of negative binomial distributions which represents over-dispersed data more efficiently. This is an extension of a univariate mixture of beta and negative binomial distributions. Characteristics of this joint distribution are studied including conditional distributions. Some properties of the correlation coefficient are explored. We demonstrate the applicability of our proposed model by fitting to three real data sets with correlated count data. A comparison is made with some previously used models to show the effectiveness of the new model.     

A test for the mean vector in large dimension and small samples

In this paper, we consider the problem of testing the mean vector in the multivariate setting where the dimension p is greater than the sample size n, namely a large p and small n problem. We propose a new scalar transform invariant test and show the asymptotic null distribution and power of the proposed test under weaker conditions than Srivastava (2009). We also present numerical studies including simulations and a real example of microarray data with comparison to existing tests developed for a large p and small n problem.     

Corporate Reputation: Do Board Characteristics Matter?

Our study draws on institutional and signalling theories to postulate relationships between board characteristics and corporate reputation. Based on a sample of 324 firms featured in Fortune's list of most admired corporations in the USA, our findings indicate that board characteristics significantly influence the assessment of firm reputation by the business community. Specifically, we found that firms with a greater proportion of outside directors and those with larger boards exhibited better reputation than those with smaller boards and a higher proportion of insiders. In addition, we observed an inverted‐U relationship between the average tenure of outside directors and corporate reputation. However, contrary to expectations, our findings indicate a negative association between independent leadership structure (i.e. absence of duality) and corporate reputation.     

New CEO Openness to Change and Strategic Persistence: The Moderating Role of Industry Characteristics

Drawing on the upper echelons, managerial discretion and strategic contingency perspectives we examine the relationships between newly chosen CEOs' openness to change and firm strategic persistence in the post-succession phase. This study is different from prior studies on the consequences of CEO succession in that it focuses on specific characteristics of the new CEO (that reflect his/her knowledge-base and cognitive orientations) and the industry context rather than purely on the event of succession. Based on a sample of 132 successions in 118 firms in the US manufacturing sector, and after controlling for industry concentration, board power, firm size and pre-succession performance, we find a negative relationship between CEOs' openness to change and post-succession strategic persistence. Interestingly, our findings indicate that this relationship is moderated by industry characteristics in that the negative association between CEO openness to change and strategic persistence is significant in high-discretion but not in low-discretion industries. Contributions of the paper to the CEO succession and strategic change literatures along with the managerial implications of our findings are discussed in the concluding section of the paper.     

Development of a score for assessing severity, predicting interventions and prognosis of musculoskeletal disorders

Musculoskeletal disorders (MSD's) are a constellation of disorders. There is no single tool available which guides the clinicians to predict the severity, intervention and recovery period of the patients who is suffering from different musculoskeletal disorder. In this paper authors tried to categorize the severity of the musculoskeletal discomfort and the prognosis of the recovery period. The questionnaire was formulated using different epidemiological risk factor of the development of MSD and the effect of MSD on physical and psychosocial factors. The questionnaire contains 13 questions which include seven direct (rating was 0, 2, 4, 6, 8 and 10) and six indirect (rating was 0, 1, 2, 3, 4 and 5) questions. Results revealed a significant correlation with the prognosis of recovery and the actual recovery period (r= 0.80). It also showed a significant correlation between the total severity score and the actual recovery (r=0.82) period. Depending on the prognosis of the recovery the severity score was segregated in four categories as mild, moderate, severe and complicated. Due to small sample size the prognosis of recovery for higher severity score could not be plotted.     

Risk factors and clinical features of text message injuries

Use of mobile phone and sending text message is a very common in today's life. While sending a text message the users need to use their thumb and other palm muscles extensively. The thumb most of the time adducted on the key pad of the mobile and use high force to type the letters. Studies in literature showed that text messaging has an adverse effect on musculoskeletal system of hand. But the extensive study on the type of disorders set in among the users who extensively use mobile phone for texting. This study aims at to evaluate risk factor and clinical feature of the MSD due to hand held devices. Twenty seven subjects participated in this study. Predefined protocols were used to evaluate type of MSD occurred among the subjects. The study revealed that development of tendinitis in extensor pollicis longus, myofascial pain syndrome (70.37%) of adductor pollicis, 1st interossei and extensor digitorum communis . Other associated problems diagnosed were thoracic outlet syndrome (51.85%), fibromyalgia syndrome (25.93%), hypothyroidism (7.41%), wrist tendinitis (14.81%) and De Quervain's syndrome (7.41%). It has been observed that the pathology were tendinitis of extensor pollicis longus, myofascial pain syndrome of thenar muscles and 1st interossei, extensor digitorum communis.     

Why employment matters: Reviving growth and reducing inequality

The global economic crisis has led to a sharp slowdown in growth and an even greater slowdown in employment creation. The resulting deterioration in the quality of employment has exacerbated the longer‐term trend of rising inequality. Jobless growth has dampened output growth through a worsening income distribution. Wages are costs on the supply side but are also incomes on the demand side, so that profit‐led growth and wage‐led growth are complements, not substitutes. Thus, growth can create jobs, while added jobs can drive growth. More employment and better jobs can also mitigate rising inequality. If macroeconomic policies focus on fostering employment creation and supporting economic growth, rather than on price stability and balanced budgets, employment would revive growth and reduce inequality.     

Unlocking the Talents‐in‐Waiting: Case Study Analysis of Chinese and Indian High‐Skilled Migrants in South Australia

Nations across the world and through time have used skilled migration mechanisms to boost economic growth and workforce competitiveness. However, effectively using these talents from abroad and transforming this collective human capital into valuable social capital is an on‐going challenge. This study applies a case study analysis of skilled migrants from China and India in South Australia and finds that there are multiple barriers to the successful integration of skilled migrants. These barriers tend to block the effective utilization of migrants’ skills and reduce the ability to advance social capital in the community. The study concludes by putting forward various policy recommendations to overcome these obstacles and outlines ideas for an effective application of a skilled migrant programme.     

Estimation with the lognormal distribution on the basis of records

Record scheme is a method to reduce the total time on test of an experiment. In this scheme, items are sequentially observed and only values smaller than all previous ones are recorded. In some situations, when the experiments are time-consuming and sometimes the items are lost during the experiment, the record scheme dominates the usual random sample scheme [M. Doostparast and N. Balakrishnan, Optimal sample size for record data and associated cost analysis for exponential distribution, J. Statist. Comput. Simul. 80(12) (2010), pp. 1389–1401]. Estimation of the mean of an exponential distribution based on record data has been treated by Samaniego and Whitaker [On estimating population characteristics from record breaking observations I. Parametric results, Naval Res. Logist. Q. 33 (1986), pp. 531–543] and Doostparast [A note on estimation based on record data, Metrika 69 (2009), pp. 69–80]. The lognormal distribution is used in a wide range of applications when the multiplicative scale is appropriate and the log-transformation removes the skew and brings about symmetry of the data distribution [N.T. Longford, Inference with the lognormal distribution, J. Statist. Plann. Inference 139 (2009), pp. 2329–2340]. In this paper, point estimates as well as confidence intervals for the unknown parameters are obtained. This will also be addressed by the Bayesian point of view. To carry out the performance of the estimators obtained, a simulation study is conducted. For illustration proposes, a real data set, due to Lawless [Statistical Models and Methods for Lifetime Data, 2nd ed., John Wiley & Sons, New York, 2003], is analysed using the procedures obtained.     

Use of Orthogonal Polynomial Approximations for Inference in Exponential Distribution Based on K-Sample Doubly Type-II Censored Data

In this article, an EM algorithm approach to obtain the maximum likelihood estimates of parameters for analyzing bivariate skew normal data with non monotone missing values is presented. A simulation study is implemented to investigate the performance of the presented algorithm. Results of an application are also reported where a Bootstrap approach is used to find the variances of the parameter estimates.