Online Intermediary as a Channel for Selling Quality‐Differentiated Services

When deciding whether to utilize an online intermediary in addition to their own distribution channels, quality differentiated service providers face the trade‐off between the benefit of extended reach and the threat of increased competition. Using an analytical framework, we analyze when and how service providers may utilize an online intermediary to their advantage in the presence of advance selling (i.e., selling a service at an early date for future consumption). In general, when an online intermediary is used, the competition effect dominates the reach effect and leads to a falling price trend. Interestingly, we find that the negative effect of increased competition on profits, due to intermediary usage, can be reversed by committing to self‐imposed participation limits (i.e., selling only a predetermined amount of services through the online intermediary). This ensures that the service provider is better off selling through both its own site and the online intermediary, rather than selling exclusively using either channel.      

中沙关系回顾与展望

中国和沙特政治制度不同,但两国发展积极友好的关系没有障碍.目前,沙特是中国在西亚和非洲最大的贸易伙伴,两国经贸合作前景广阔.同时,中沙双方均奉行独立自主的外交政策,拥有良好的政治关系,未来在区域组织和联合国等国际舞台上将有更广泛的合作领域.     

Image segmentation using voronoi polygons and MCMC, with application to muscle fibre images

We investigate a Bayesian method for the segmentation of muscle fibre images. The images are reasonably well approximated by a Dirichlet tessellation, and so we use a deformable template model based on Voronoi polygons to represent the segmented image. We consider various prior distributions for the parameters and suggest an appropriate likelihood. Following the Bayesian paradigm, the mathematical form for the posterior distribution is obtained (up to an integrating constant). We introduce a Metropolis-Hastings algorithm and a reversible jump Markov chain Monte Carlo algorithm (RJMCMC) for simulation from the posterior when the number of polygons is fixed or unknown. The particular moves in the RJMCMC algorithm are birth, death and position/colour changes of the point process which determines the location of the polygons. Segmentation of the true image was carried out using the estimated posterior mode and posterior mean. A simulation study is presented which is helpful for tuning the hyperparameters and to assess the accuracy. The algorithms work well on a real image of a muscle fibre cross-section image, and an additional parameter, which models the boundaries of the muscle fibres, is included in the final model.     

American families: trends and correlates

Discussion focused on the nature of the roles of the family, a review of the major demographic changes (marriage, cohabitation, nonfamily households, remarriage, fertility, teenage pregnancy, and female employment) affecting the American family in the past decades, and the nature of the impact on women, men, and children. There were four major trends identified: 1) increased proportions of children living in single-parent families due to high rates of divorce and increased childbearing outside of marriage; 2) increased proportions of adults in nontraditional living arrangements; 3) increased female labor force participation during all stages of the life cycle; and 4) decreased proportions of children and increased proportions of older people out of total population due to declining mortality and fertility rates. Family formation arises out of childbearing and childrearing roles, the need for companionship and emotional support, and the opportunities for specialization and trade, and the economies of scale. The costs of family living may include the potential for disagreement, conflict, loss of privacy, and time and money. There were a number of reasons identified for not maintaining traditional families consisting of a married couple with children. The trends were for later age at marriage: 24.4 years in 1992 for women, increased cohabitation (almost 50% cohabiting prior to first marriage in 1985-86), decreased number of married couple households, and increased number of adults in non-family households. The divorce rate has risen over the past 100 years with peaks in the 1970s; the reasons were identified as increased baby boomers and new marriages, increased labor participation of women, and changes in gender roles. The stabilization and slight decline in rates may be due to a natural leveling, the likelihood of greater stability within new marriages, and the aging of the baby boomers. An anticipated increase in divorce rates in the future was also justified. Remarriage rates varied by gender, age at separation/divorce, presence of children, race/ethnicity, and education. Fertility remained stable at 1.8 during the late 1970s and early 1980s and increased slightly to 2.0 in 1989. IN 1990, there were 25% out-of-wedlock births compared to 5% in 1960. About 12% of births in 1989 were to teenagers. There has been an increase in female-headed households, the median income of which in 1992 was $13,012, or 33% of married couple income.     

On a further generalization of the savage test

A statistic based on the frequencies within the k+1 intervals specified by k arbitrary quantiles is proposed for a LMP test against Lehmann alternatives generalizing the Savage test for the two-sample problem. The maximum efficiency relative to the Savage test for optimally chosen k quantiles is also provided for k=l(2)l5. The asymptotic normality of the statistic follows from the asymptotic multinomial distribution of the frequencies in the classes determined by the k quantiles.     

Predictive Influence of Unavailable Values of Future Explanatory Variables in a Linear Model

We consider an approach to prediction in linear model when values of the future explanatory variables are unavailable, we predict a future response y ^f at a future sample point x ^f when some components of x ^f are unavailable. We consider both the cases where x ^f are dependent and independent but normally distributed. A Taylor expansion is used to derive an approximation to the predictive density, and the influence of missing future explanatory variables (the loss or discrepancy) is assessed using the Kullback–Leibler measure of divergence. This discrepancy is compared in different scenarios including the situation where the missing variables are dropped entirely.     

Are rural–urban migrants living in urban slums more vulnerable in terms of housing,health knowledge,smoking, mental health and general health?

The magnitude of rural–urban migration in Bangladesh is increasing. Rapid urbanisation and a growing number of slums (dominated by migrants) pose many challenges to health. To our knowledge, studies regarding internal migration and health are scarce and results are mixed. Therefore, we compared several aspects, namely: housing, health knowledge, smoking, mental and general health, for three groups of migrants, designated urban natives/urban to urban migrants (UN/UU), rural to urban migrants (RU) and rural natives/rural to rural migrants (RN/RR). Results based on a sample of 5,136 adults indicated that the majority of respondents were less than 50 years old, female, married and uneducated. The percentages of UN/UU, RU and RN/RR migrants were 9.6, 69.2 and 21.3, respectively. As both bivariable and multivariable analyses indicated greater vulnerability among RU migrants in terms of the above‐mentioned aspects, this particular group deserves more attention from policy‐makers and other stakeholders. Some implications are also discussed. Key Practitioner Message: ● This study provides information regarding internal migration and explains push–pull factors in Bangladesh; ● It provides evidence regarding greater vulnerability in terms of health and other determinants among rural–urban migrants living in Dhaka slums; ● Lastly, the study justifies the importance of intervention strategies targeting poor migrants in urban slums in developing countries.     

Confidence intervals for the mean and a percentile based on zero-inflated lognormal data

The problems of estimating the mean and an upper percentile of a lognormal population with nonnegative values are considered. For estimating the mean of a such population based on data that include zeros, a simple confidence interval (CI) that is obtained by modifying Tian's [Inferences on the mean of zero-inflated lognormal data: the generalized variable approach. Stat Med. 2005;24:3223—3232] generalized CI, is proposed. A fiducial upper confidence limit (UCL) and a closed-form approximate UCL for an upper percentile are developed. Our simulation studies indicate that the proposed methods are very satisfactory in terms of coverage probability and precision, and better than existing methods for maintaining balanced tail error rates. The proposed CI and the UCL are simple and easy to calculate. All the methods considered are illustrated using samples of data involving airborne chlorine concentrations and data on diagnostic test costs.     

An insight into technology diffusion of tractor through Weibull growth model

Most of the technological innovation diffusion follows an S-shaped curve. But, in many practical situations this may not hold true. To this end, Weibull model was proposed to capture the diffusion of new technological innovation, which does not follow any specific pattern. Nonlinear growth models play a very important role in getting an insight into the underlying mechanism. These models are generally ‘mechanistic’ as the parameters have meaningful interpretation. The nonlinear method of estimation of parameters of Weibull model fails to converge. Taking this problem into consideration, we propose the use of a powerful technique of genetic algorithm for parameter estimation. The methodology is also validated by simulation study to check whether parameter estimates are closer to the real value. For illustration purpose, we model the tractor density time-series data of India as a whole and some major states of India. It is seen that fitted Weibull model is able to capture the technology diffusion process in a reasonable manner. Further, comparison is also made with Logistic and Gompertz model; and is found to perform better for the data sets under consideration.