This paper proposes an exponentially weighted moving average (EWMA) control chart that is capable of detecting changes in both process mean and standard deviation for autocorrelated data (referred to as the Maximum Exponentially
Weighted Moving Average Chart for Autocorrelated Process, or MEWMAP chart).
This chart is based on fitting a time series model to the data, and then calculating the
residuals. The observations are represented as a first-order autoregressive process plus a random error term. The Average Run Lengths (ARLs) for fixed decision intervals and reference values (h, k) are calculated. The proposed chart is compared with the Max-CUSUM chart for autocorrelated data proposed by Thaga (2003).
Comparisons are based on the out-of-control ARLs. The MEWMAP chart detects moderate to large shifts in the mean and/or standard deviation at both low and high levels of autocorrelations more quickly than the Max-CUSUM chart for autocorrelated processes.
Die navorsing stel voor dat 'n eksponensiaal geweegde bewegende gemiddelde
kontrolekaart gebruik word om verandering van prosesgemiddelde en –standaardafwyking van outogekorreleerde data te bepaal. Die kontrolekaart word gedryf deur passing van 'n tydreeks as datamodel met bepaling van residuwaardes.
Met hierdie gegewens as vertrekpunt word gemiddelde looplengtes vir vaste
besluitintervalle en verwysingwaardes (h, k) bereken. Die kontrolekaart bepaal matige en groot verskuiwings van waardes vir hoë en lae outokorrelasiewaardes heel snel.
Masoumi Karakani, Hossein(University of Pretoria, 2020)
Statistical process control (SPC) is a collection of scientific tools developed and engineered to diagnose unnecessary variation in the output of a production process and eliminate it or perhaps accommodate it by adjusting ...
Adam, Sumaiya; Lombaard, H.A.D.T. (Hennie); Van Zyl, Danie G.(Health and Medical Publishing Group, 2014-10)
BACKGROUND. Diabetes in pregnancy is associated with both accelerated fetal growth and intrauterine growth restriction.
OBJECTIVE. To compare the difference in occurrence of large-for-gestational-age (LGA) and ...
Chakraborti, Subhabrata; Graham, Marien Alet(Taylor and Francis, 2019)
Control charts that are based on assumption(s) of a specific form for the underlying process distribution are referred to as parametric control charts. There are many applications where there is insufficient information ...