The Shewhart X¯- and S-charts are most commonly used for monitoring the process mean variability based on assumption of normality. However, many distributions may follow a positively skewed distribution, such as lognormal distribution. In this study, we discuss construction three combined jointly standard deviation. simulation results show that more effective when distribution is skewed. A real...

independence of observations is a fundamental assumption in designing an x chart for individual observations. but unfortunately, the assumption of existence of independent data is not even approximately satisfied. in fact, there is one kind of autocorrelation in the data. this paper demonstrates, through simulating an ar(1) process, that the autocorrelation in the data has deep effect on x char...

The standard deviation of column ozone from the zonal mean (COSDZ) provides a measure of the longitudinal inhomogeneity in ozone and dynamical wave activities in the atmosphere. Using the Total Ozone Mapping Spectrometer (TOMS) data, we obtain latitude-season maps of COSDZ that are representative of a dynamically quiet year (1987) and a dynamically active year (1992). The spatial and temporal p...