A new double sampling control chart for monitoring process mean using auxiliary information

Statistical quality control charts have been widely accepted as a potentially powerful process monitoring tool because of their excellent speed in tracking shifts in the underlying process parameter(s). In recent studies, auxiliary-information-based (AIB) control charts have shown superior run length performances than those constructed without using it. In this paper, a new double sampling (DS) control chart is constructed whose plotting-statistics requires information on the study variable and on any correlated auxiliary variable for efficiently monitoring the process mean, namely AIB DS chart. The AIB DS chart also encompasses the classical DS chart. We discuss in detail the construction, optimal design, run length profiles, and the performance evaluations of the proposed chart. It turns out that the AIB DS chart performs uniformly better than the DS chart when detecting different kinds of shifts in the process mean. It is also more sensitive than the classical synthetic and AIB synthetic charts when detecting a particular shift in the process mean. Moreover, with some realistic beliefs, the proposed chart outperforms the exponentially weighted moving average chart. An illustrative example is also presented to explain the working and implementation of the proposed chart.     

Double sampling |S| control chart with variable sample size and variable sampling interval

This study presents a control chart for monitoring shifts in the covariance matrix of a multivariate normally distributed process. This chart combines the double sampling, variable sample size and variable sampling interval features, and is called the DSVSSI |S| chart. A Markov chain approach is developed to design the DSVSSI |S| chart, by minimizing the average time to signal (ATS), for a specified shift size in the covariance matrix. The DSVSSI |S| chart has a better ATS performance compared to other existing charts. An example is given to illustrate the operation of the DSVSSI |S| chart.     

Bridging the Gap: An Exploratory Study of Corporate Social Responsibility among SMEs in Singapore

Corporate social responsibility (CSR) among small-medium enterprises (SME) is an overlooked area, despite the latter's emerging prominence as an economic player. To provide a comprehensive analysis of the CSR landscape among Singapore SMEs, a triangulation of 15 in-depth interviews and a self-administered Web survey was conducted among 113 senior executives from top 500 Singapore SMEs (27.2% response). Key findings include (a) moderate awareness but low comprehension of CSR; (b) engagement relevance to immediate stakeholders; (c) individual values, stakeholder relationships, and governmental influences as main drivers; and (d) lack of various resources as key barriers. Implications and future research directions are discussed.     

Physical and mental health changes in aging foster parents: Do child behavioural problems hasten declines?

This study examined foster parent physical and mental health over time. It was hypothesized that increased severity and frequency of child behavioural problems, whether externalizing or internalizing, would be associated with poorer health over time, especially for foster parents ≥60 years of age. Data from the baseline and Wave 2 interview of the 2010 National Survey of Child and Adolescent Well‐Being were used. The final analytic sample included kin and nonkin foster parents who had custody of a foster child for both waves of data collection (n = 962). Ordinary Least Squares regression models with lagged dependent variables showed that foster parents ≥60 had deteriorating physical health over time, but caregiver age alone had no association with worsening mental health. However, parents ≥60 caring for children with externalizing behavioural problems had significantly improved physical health. Mental health of parents ≥60 significantly diminished if child externalizing or internalizing problems worsened. Findings indicate that for aging foster parents, externalizing child behaviours may stimulate physical activity and improved physical health, yet any type of child behavioural problem can deteriorate mental health functioning.     

Forecasting the spot price of gold:combined forecast approaches versus a composite forecast approach

The fluctuation of the gold price has significant impact on the economic and social aspects of a society. In the literature, most authors have employed fundamental analysis approach in forecast model building. The basic principle underlying this approach is that it is the supply and the demand which simultaneously determines the gold price. However, due to the lack of data of quantity supplied and quantity demanded, simultaneous econometric approach seems unsuccessful. In this paper, combined and composite time series forecasting techniques are proposed. The effects of various economic factors towards spot price of gold are also examined. Among the combined forecasting models, it seems that the odds-matrix method of assigning weights provides the most accurate forecasts of spot price of gold. For the economic factors considered, the futures price of gold and and the exchange rate seem to be most informative in forecasting the spot price of gold.     

Combined double sampling and variable sampling interval np chart

A combined double sampling and variable sampling interval (DSVSI) np chart is investigated in this study. The optimal design of the DSVSI np chart is based on minimizing the out-of-control average time to signal. From the numerical results, the DSVSI np chart performs reasonably well in comparison with the standard np chart, double sampling np chart, synthetic double sampling np chart, and other existing np type control charts for detecting increases in the process of fraction non conforming, based on the zero-state case. An example is provided to illustrate the application of the DSVSI np chart.     

A new non-parametric multivariate EWMA sign control chart for monitoring process dispersion

In this paper, a new non-parametric multivariate exponentially weighted moving average (NMEWMA) sign chart is proposed for monitoring the process dispersion. The run length characteristics of the NMEWMA sign chart are computed with the help of Markov chain and Monte Carlo simulations. Moreover, the NMEWMA sign chart is also used to detect changes in the process mean and dispersion simultaneously. An illustrative example is also used to explain the implementation of proposed control chart.     

The double sampling S2 chart with estimated process variance

This paper proposes useful exact bounds for the parameters of the double sampling S² chart with known process variance and it also investigates the properties of the double sampling S² chart with estimated process variance, in terms of the average run length, the standard deviation of the run length and the average sample size, providing a numerical comparison with the known process variance case. It also provides guidelines to systematically design the double sampling S² chart both with known and estimated process variance and proposes two optimal design procedures with estimated process variance, for (a) minimizing the out-of-control average run length and (b) minimizing the out-of-control average sample size.