Exponentially weighed moving average charts for monitoring zero-inflated proportions with applications in health care.

In the context of public health surveillance, the aim is to monitor the occurrence of health-related events. Among them, statistical process monitoring focuses very often on the monitoring of rates and proportions (i.e. values in (0,1)) such as the proportion of patients with a specific disease. A popular control chart that is able to detect quickly small to moderate shifts in process parameters is the exponentially weighed moving average control chart. There are various models that are used to describe values in (0,1). However, especially in the case of rare health events, zero values occur very frequently which, for example, denote the absence of the disease. In this paper, we study the performance and the statistical design of exponentially weighed moving average control charts for monitoring proportions that arise in a health-related framework. The proposed chart is based on the zero-inflated Beta distribution, a mixed (discrete-continuous) distribution, suitable for modelling data in [0,1). We use a Markov chain method to study the run length distribution of the exponentially weighed moving average chart. Also, we investigate the statistical design as well as the performance of the proposed charts. Comparisons with a Shewhart-type chart are also given. Finally, we provide an example for the practical implementation of the proposed charts.

Analysis on under-5 mortality rate and the leading kinds of diseases in China, from 2000 to 2006 / 中华流行病学杂志

Objective To study the changing pattern of infant mortality and under-5 mortality rate in China from 2000 to 2006, and to evaluate China's progress in achieving the United Nations' Millennium Development Goal 4. Methods A population-based survey was conducted through a nationwide multi-level surveillance network. The mortality rate and the proportion of death for children under 5 were analyzed. Results The infant mortality rate (IMR), under-5 mortality rate (U5MR) in China dropped to 17.2, 20.6 per 1000 live births in 2006, respectively, comparing to 32.2 and 39.7 per 1000 live births in 2000. In urban areas, IMR, U5MR dropped to 8.0, 9.6 per 1000 live births in 2006, respectively while they were 11.8 and 13.8 per 1000 live births respectively in 2000. In rural areas, IMR, USMR dropped to 19.7 and 23.6 per 1000 live births in 2006, respectively but they were 37.0 and 45.7 per 1000 live births respectively in 2000. During this period, the mortality rates due to pneumonia and diarrhea had dropped sharply. The proportion of deaths due to pneumonia, diarrhea also dropped from 19.5%, 4.9% in 2000 to 15.6%, 3.7% in 2006, respectively. In urban areas, the proportion of deaths due to pneumonia dropped from 9.9% in 2000 to 9.8% in 2006, In rural areas, the proportion of deaths due to pneumonia, diarrhea dropped from 20.1%, 5.2% in 2000 to 16.2%, 4.0% in 2006, respectively. Conclusion The U5MR in China remarkably dropped from 2000 to 2006. Based on data through the surveillance program, China should be able to accomplish the Millennium Development Goals 4 of the United Nations as planned.