Abstract:
The main goal of this research is to study Statistical Process Control (SPC) with
Exponentially Weighted Moving Average (EWMA) control chart for detecting changes in
process mean. The characteristic of control chart is Average Run Length (ARL) which is
the average number of samples taken before an action signal is given. Ideally, an
acceptable ARL of in-control process should be enough large, so-called ( ARL0 ).
Otherwise it should be small when the process is out-of-control, so-called Average of
Delay Time ( ARL1 ) or a mean of true alarm. We obtain explicit formulas of ARL for
EWMA chart for Autoregressive and Moving Average (ARMA) processes with Exponential
white noise. The explicit formulas for ARL have been found to be accurate, fast and easy
to calculate. In particular, the explicit analytical formulas for evaluating ARL0 and 1 ARL
be able to get a set of optimal parameters which depend on smoothing parameter and width of control limit ( H ) for designing EWMA chart with minimum of ARL1 .