Statistical measurement of the inventory shortage cost

In searching for the optimal inventory control policy, the objective is to minimize the expected total costs related, of which the shortage cost is an important element. Due to the difficulty in calculating the indirect cost of the loss of goodwill resulted from the shortage, practitioners and researchers often simply assume a fixed penalty cost on the inventory shortage or switch to the alternative method by assigning a specific customer service level. The development of an appropriate tool for measuring the shortage cost can help a business control the total costs and improve the productivity more effectively. This paper proposes probabilistic measurements of the shortage cost, based on mathematical relationship between the cost and the shortage amount. The derived closed-form estimates of the expected shortage cost value can then be applied to support the determination of the optimal inventory control policy.     

Optimal design of the adaptive exponentially weighted moving average control chart over a range of mean shifts

The adaptive exponentially weighted moving average (AEWMA) control chart is a smooth combination of the Shewhart and exponentially weighted moving average (EWMA) control charts. This chart was proposed by Cappizzi and Masarotto (2003) to achieve a reasonable performance for both small and large shifts. Cappizzi and Masarotto (2003) used a pair of shifts in designing their control chart. In this study, however, the process mean shift is considered as a random variable with a certain probability distribution and the AEWMA control chart is optimized for a wide range of mean shifts according to that probability distribution and not just for a pair of shifts. Using the Markov chain technique, the results show that the new optimization design can improve the performance of the AEWMA control chart from an overall point of view relative to the various designs presented by Cappizzi and Masarotto (2003). Optimal design parameters that achieve the desired in-control average run length (ARL) are computed in several cases and formulas used to find approximately their values are given. Using these formulas, the practitioner can compute the optimal design parameters corresponding to any desired in-control ARL without the need to apply the optimization procedure. The results obtained by these formulas are very promising and would particularly facilitate the design of the AEWMA control chart for any in-control ARL value.     

On robustness of the Shiryaev–Roberts change-point detection procedure under parameter misspecification in the post-change distribution

The gist of the quickest change-point detection problem is to detect the presence of a change in the statistical behavior of a series of sequentially made observations, and do so in an optimal detection-speed-versus-“false-positive”-risk manner. When optimality is understood either in the generalized Bayesian sense or as defined in Shiryaev's multi-cyclic setup, the so-called Shiryaev–Roberts (SR) detection procedure is known to be the “best one can do”, provided, however, that the observations’ pre- and post-change distributions are both fully specified. We consider a more realistic setup, viz. one where the post-change distribution is assumed known only up to a parameter, so that the latter may be misspecified. The question of interest is the sensitivity (or robustness) of the otherwise “best” SR procedure with respect to a possible misspecification of the post-change distribution parameter. To answer this question, we provide a case study where, in a specific Gaussian scenario, we allow the SR procedure to be “out of tune” in the way of the post-change distribution parameter, and numerically assess the effect of the “mistuning” on Shiryaev's (multi-cyclic) Stationary Average Detection Delay delivered by the SR procedure. The comprehensive quantitative robustness characterization of the SR procedure obtained in the study can be used to develop the respective theory as well as to provide a rational for practical design of the SR procedure. The overall qualitative conclusion of the study is an expected one: the SR procedure is less (more) robust for less (more) contrast changes and for lower (higher) levels of the false alarm risk.     

Monotonic change point estimation of generalized linear model-based regression profiles

In this article, a maximum likelihood estimator is derived in the generalized linear model-based regression profiles under monotonic change in Phase II. The performance of the proposed estimator is comprehensively investigated through some special cases, and compared with estimators under step change and drift. The results show that the proposed estimator has better performance in small and medium shifts under different increasing changes. Finally, the applicability of the proposed estimator is illustrated using a real case.     

Exponentially weighted moving average charts for correlated multivariate Poisson processes

In this article, we study exponentially weighted moving average (EWMA) control schemes to monitor the multivariate Poisson distribution with a general covariance structure, so that the practitioner can simultaneously monitor multiple correlated attribute processes more effectively. The statistical performance of the charts is assessed in terms of the run length properties and compared against other mainstream attribute control schemes. The application of the proposed methods to real-life and simulated datasets is demonstrated.     

Investigating the differential mobility experiences of Chinese cross-border students

Recent migration studies have adopted the lens of mobility to examine the stratifying effects of border policies, but few investigate the differential mobility of migrant families and children. This paper aims to contribute to the migration literature by considering the interplay between border policies, family configurations, and differential mobility. We apply the lens of differential mobility to the experiences of Chinese cross-border pupils – young child migrants with Hong Kong permanent residency who reside in Shenzhen, China, and cross the border to attend school. We begin by describing shifts in Hong Kong’s border and immigration policies since 1997, which have created a typology of families differentiated by mixed status, citizenship rights, and mobility. We then turn to four case studies of students with unequal border-crossing experiences to elucidate how border control constrains or promotes family mobility and perpetuates inequalities.     

The classing gaze and its gendering effects: (dis)‐respectability,emotional (in)‐competency,and the counselling experiences of domestically violent Taiwanese men

Research on domestically violent men typically takes an oppositional logic of gender. While the significance of class in researching domestically violent men is identified, class and gender are often treated as separate entities that do not complicate each other. Drawing upon group observations and in‐depth interviews, this paper identifies how intersections of class and gender manifest in the counselling experiences of domestically violent Taiwanese men. From a Bourdieusian feminist analysis, the authors analyse (1) how class distinctions serve to (re)produce gendered hierarchy; (2) how contradictory experiences of gender reveal a relational understanding of class; and (3) how the gendered nature of domestically violent men is inscribed with a meaning of (working) class specificity for maintaining middle‐class ‘purity’. In analysing men's multiple and conflicting experiences, this paper contributes to research on domestically violent men by showing how class and gender are actively constructed and not produced in a monolithic/invariant way.     

Implementing Rigorous Survey Methodology within Contexts of Social Work Education,Training and Practice: A Case Study in Substance Use

With the integration of evidence-based practice central to all areas of social work education and training across the globe, it is crucial that we continue to engage with the methodological challenges inherent in gathering this evidence, particularly when it is related to the nature of social work education itself. As a result, this paper addresses some of the methodological challenges involved in examining the education available to social workers on engaging with substance use, both within the social work academy and local authorities in England. Drawing on experiences of implementing large scale online surveys from three substantial research projects completed by the authors, this paper highlights four methodological themes: (1) Constructing a representative sampling frame; (2) Identifying participants within organisations with many departments; (3) Response rates; and (4) Questionnaire design. While these are familiar methodological considerations, this article draws attention to the specific complexities of gathering ‘representative’ knowledge to inform educational strategies on substance use within social work education and employment contexts. Finally this paper offers lessons learned and guidance for social work academics, students and practitioners who are minded to build, or draw from, an evidence-base using representative samples from and within these environments.