Estimating a restricted normal mean

Let X ₁, X ₂, ..., X _n be a random sample from a normal distribution with unknown mean μ and known variance σ ². In many practical situations, μ is known a priori to be restricted to a bounded interval, say [−m, m] for some m > 0. The sample mean , then, becomes an inadmissible estimator for μ. It is also not minimax with respect to the squared error loss function. Minimax and other estimators for this problem have been studied by Casella and Strawderman (Ann Stat 9:870–878, 1981), Bickel (Ann Stat 9:1301–1309, 1981) and Gatsonis et al. (Stat Prob Lett 6:21–30, 1987) etc. In this paper, we obtain some new estimators for μ. The case when the variance σ ² is unknown is also studied and various estimators for μ are proposed. Risk performance of all estimators is numerically compared for both the cases when σ ² may be known and unknown.     

Bronchodilator reliever use and its association with the economic and humanistic burden of COPD: a propensity-matched study

Background and aims: Short-acting bronchodilators are normally used as supplemental relief medication for breakthrough symptoms in COPD patients. The objective of this cross-sectional study was to assess if more frequent vs infrequent use of relief medication in maintenance-treated COPD patients, split by the severity dyspnea, was associated with an increase in the overall disease burden.

Methods: A population-based cross-sectional survey (Adelphi DSP) was conducted among patients with COPD in five European countries. Information was collected on demographic and clinical characteristics, reliever inhaler use, dyspnea (mMRC), health status (CAT, EQ-5D), sleep quality (JSEQ) and healthcare resource use including moderate–severe COPD exacerbations, physician visits, COPD medications and other COPD related resources. The humanistic and economic burden was compared between patients with infrequent reliever use (<1 occasion/week) and more frequent use (≥ 1 occasion/week). The association between increased reliever use and economic burden was also examined after matching patients based on propensity-scores balancing demographic and disease burden characteristics.

Results: Among the 1373 COPD patients prescribed a reliever inhaler, 29% reported using reliever medication ≥1 occasion/week. In the unmatched cohort, more frequent reliever use (n?=?377) compared to infrequent use (n?=?996) was linked to poorer health status (CAT: 25.7 vs 20.0; p?p?p?p?p?=?.0001). In the propensity-score matched population, more frequent reliever use was also associated with significantly higher annual costs for COPD management (€5,034 vs €3,705, p?=?.0327) compared to patients with infrequent reliever use.

Conclusion: In moderate-to-severe COPD, more frequent reliever use is associated with increased exacerbation risk and increased management costs.     

From Fatwallet to eBay: An investigation of online deal-forums and sales promotions

Sales promotions are an important part of retail advertising strategy. Traditionally, research on sales promotions has generally assumed that the buyers are end consumers who do not engage in reselling, in large part due to high transaction costs. However, the recent Internet related technologies have dramatically lowered the cost of transferring goods between consumers, leading to relative ease of reselling activity amongst individual consumers. Little is known about the impact of this phenomenon on retailer's sales promotion strategy. In this research we investigate the reselling activity in online auctions for products that active deal seekers can obtain at deeply discounted prices from retailers. We further investigate the role of deal-forums in the resale process. Data is collected from an online deal-forum (http://www.fatwallet.com/) and eBay to test various reselling-related hypotheses. The results show that there is a significant abnormal increase in the number of newly posted auctions of a product after the deal information of this product is posted on deal-forum website. We also find that there is a significant price incentive for individuals to resell. The implications for sales promotion research and practice are discussed.     

Gender differences in the effect of downward influence strategies on perceived stress and general-health: The mediating role of organizational justice

This study examined the effects of supervisor’s downward influence strategies (DIS) on subordinates’ perceived stress and general-health. The influencing effects of DIS were also analyzed in the light of the mediating effects of organizational justice dimensions, namely, distributive justice (DJ), procedural justice (PJ) and interactional justice (IJ). Responses were collected from three organizations through survey method (Males, N = 91; females, N = 74). Gender differences were observed in the perceptions of DIS which affected perceived stress and general-health conditions of both male and female employees. Further, the results revealed that supervisor’s task-oriented DIS (e.g., negative sanctions) increase perceived stress and negative health conditions in both genders. Supervisor’s people-oriented DIS (e.g., ingratiation) lowered perceived stress and triggered botheration-free existence in the employees. The mediation analysis of justice dimensions indicated that, in the case of males, IJ and PJ positively mediate people-oriented DIS effects on stress and general health. However, in females, supervisor’s ingratiation and positive sanctions helped in ameliorating stress through their positive PJ perceptions. Strong indirect effects of supervisor’s task-oriented strategy (e.g., rationality) were observed on male’s stress and general-health through IJ. On the other hand, supervisor’s rationality and assertiveness reduced female employees’ perceived stress through their PJ and DJ perceptions, respectively.     

Assessing volatility transmission between Brent and stocks in the major global oil producers and consumers – the multiscale robust quantile regression

This paper investigates the volatility transmission effect between Brent oil futures and stock markets in the major global oil producing and consuming countries – the U.S., Russia, China and Saudi Arabia. In that process, we employ a mixture of novel and elaborate methodologies – wavelet signal decomposing procedure, GARCH model with complex distribution and recently developed robust quantile regression. Our results indicate that the effect is stronger in short-term horizon than in midterm and long-term in most cases. The magnitude is much stronger in turbulent times, whereas in tranquil times, this effect is very weak. We find that Russian RTS index endures the strongest volatility transmission effect from oil market. Surprisingly, Saudi stock market does not suffer heavy spillover effect even in the periods of increased market unrest. In the U.S. and China, the effect is much stronger from stocks to oil than vice-versa, and this particularly applies for the U.S. case.

     

A correlation study of sustainable development goal (SDG) interactions

Quality & Quantity - As universities are the change agent of society, institutions from all nations set their goals to transform the world by exploring various societal challenges that humans...