Exponentially weighted moving average control charts for three-level products

In this paper, exponentially weighted moving average (EWMA) control charts for multinomial data are developed with a three-level classification scheme. The lower and upper control limits of the proposed EWMA control chart are evaluated using Markov chain approximation. Compared with the three-level Shewhart control chart, numerical results indicate that the proposed EWMA control chart is relatively sensitive to small shifts in a three-level multinomial process. A figure and a table are provided for practitioners to select the value of chart limit coefficient that gives the desired in-control average run length.     

Designing Variables Sampling Plans with Process Loss Consideration

For the implementation of an acceptance sampling plan, a problem the quality practitioners have to deal with is the determination of the critical acceptance values and inspection sample sizes that provide the desired levels of protection to both vendors and buyers. Traditionally, most acceptance sampling plans focus on the percentage of defective products instead of considering the process loss, which doesn't distinguish among the products that fall within the specification limits. However, the quality between products that fall within the specification limits may be very different. So how to design an acceptance sampling plan with process loss consideration is necessary. In this article, a variables sampling plan based on L _e is proposed to handle processes requiring low process loss. The required sample sizes n and the critical acceptance value c with various combination of acceptance quality level are tabulated. The proposed sampling plan provides a feasible policy, which can be applied to products requiring low process loss where classical sampling plans cannot be applied.     

A New Nonparametric Test for the Umbrella Alternative Problem

In this article, we propose a new nonparametric test for detecting umbrella alternatives. It is designed to improve the power of Pan (1996 Pan , G. ( 1996 ). Distribution-free tests for umbrella alternatives . Communications in Statistics—Theory and Methods 25 ( 12 ): 3185 – 3194 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar])'s test, which is based on the breakdown of umbrella alternatives into a union of simple-ordered alternatives. Distribution-free tests are proposed in the case where the peak of the umbrella is unknown. Some actual data examples and the results of a Monte Carlo power study are also discussed.     

Does smoking have a causal effect on weight reduction?

This study examines the relationship between smoking and body mass index (BMI) with a simultaneous equations system allowing for censoring and endogeneity of the number of cigarettes smoked, which alleviates simultaneity bias caused by unobserved heterogeneity and expansion bias by censoring in the regressor. The results suggest smoking may not have a strong long-term causal effect on body weight after controlling for the endogeneity. The negative relationship between smoking and BMI reported in the literature is potentially attributable to the aforementioned biases and should be interpreted with caution. The statistical procedure developed can be useful in other applications with a censored endogenous regressor.

Queue hurdle Coxian phase-type model for two-stage process of population-based cancer screening

Statistical Methods & Applications - The quality assurance of two-stage population-based cancer screening program is determined by arrival rate (attending screening), positive rate (determined...