Adaptive sample size and sampling intervals schemes have been widely used to improve the statistical efficiency of Hotelling T control chart in detecting small changes when the quality of a product or a process can be characterised by the multivariate distribution of quality characteristics. In this paper, we design a Hotelling T scheme varying sample sizes and sampling intervals (VSSI-T) for a...

The combination of Shewhart control charts and an exponentially weighted moving average (EWMA) control charts to simultaneously monitor shifts in the mean output of a production process has proven very effective in handling both small and large shifts. To improve the sensitivity of the control chart to detect off-target processes, we propose a combined Shewhart-EWMA (CSEWMA) control chart for m...

Background and objectives: Risk-adjusted Bernoulli control chart is one of the main tools for monitoring multistage healthcare processes to achieve higher performance and effectiveness in healthcare settings. Using parameter estimates can lead to significantly deteriorate chart performance. However, so far, the effect of estimation error on this chart in which healthcare ...

In order to examine the accuracy of large amount of the field survey data with less accurate, an examination method based on multi-resolution satellite images was proposed in this paper. As there were so large amount of data, stratified random sampling was used to obtain effective samples. Firstly, vegetation index derived from low-resolution satellite images at different times has been adopted...

The performance of an X-bar chart is usually studied under the assumption that the process standard deviation is well estimated and does not change. This is, of course, not always the case in practice and X-bar charts are not robust against errors in estimating the process standard deviation or changing standard deviation. In this paper, the use of an exponentially weighted moving average (EWMA...

The significant features of Tukey’s control chart include characteristics such as: easy setup, use of single observation to monitor process, and suitability to monitor destructive testing processes. The control limit width and sampling interval should be determined before Tukey’s control chart can be used. In this study, Duncan’s cost function is modified to construct an economic design model o...

purpose: to evaluate the effect of levodopa-carbidopa on improvement of visual acuity, color vision, and visual field in patients with nonarteritic anterior ischemic optic neuropathy (naion) with onset less than 6 wks. methods: in this double-blind randomized controlled trial, 13 patients were treated with levodopa-carbidopa and 12 patients were treated with placebo for 3 weeks. after 6 months,...

The control charts are graphical tools and proven techniques to improve the performance of a process. Usually, the processes are not naturally controlled, so the use of control charts will help to reduce the variability and increase the stability of the process. In the traditional approach, control charts with fix sample size and constant sampling intervals were used to identify the changes in ...