Control charts are extensively used in many real world applications. Since process parameters are rarely known, common practice is to estimate them. Then, the control limits are modified and become actually random variables. In this paper, we deal with the univariate control charts for...

In this paper, some new indices for ordinal data are introduced. These indices have been developed so as to measure the degree of concentration on the “small” or the “large” values of a variable whose level of measurement is ordinal. Their advantage in relation to other approached is...

The EWMA control chart is used to detect small shifts in a process. It has been shown that, for certain values of the smoothing parameter, the EWMA chart for the mean is robust to non normality. In this article, we examine the case of non normality in the EWMA charts for the dispersion. It is...

This paper assesses the link between exchange volatility and exports in Egypt by combining wavelet analysis with an optimal GARCH model chosen among various extensions. The observed outcomes reveal that this relationship is complex and depends then widely to frequency-to-frequency variation and...

How does inflation uncertainty interact with inflation rate? The purpose of this article is to assess this question in Egypt in a wavelets transform framework. We investigate the direction of causality in the relationship inflation-inflation uncertainty by combining component GARCH model,...

The nexus between inflation and its uncertainty has been a topic of wide dispute. Using wavelet decomposition and with special reference to Egypt for the period 1960-2013, we find that the focal relationship varies substantially among the different frequencies involved. In the short-run,...

To effectively assess the link between exchange rate uncertainty and exports performance in Egypt, this article relies on an optimal GARCH model among decomposed series on a scale-by-scale basis via wavelet approach. The observed outcomes reveal that the focal connection depends substantially on...

The present study addresses one of the most problematic phenomena: Bitcoin price. We explore the Granger causality for two relationships (Bitcoin price and transactions; Bitcoin price and investors’ attractiveness) from a frequency domain perspective using Breitung and Candelon’s (2006)...

Control charts are extensively used in many real world applications. Since process parameters are rarely known common practice is to estimate them. Then, the control limits are modified and become actually random variables. In this paper, we deal with the univariate control charts for dispersion...

The identification of the out of control variable, or variables, after a multivariate control chart signals, is an appealing subject for many researchers in the last years. In this paper we propose a new method for approaching this problem based on principal components analysis. Theoretical...