Information Technology Journal1812-56381812-5646Asian Network for Scientific Information10.3923/itj.2014.2369.2373ZhangLi SongXiangdong 1220141314In order to reduce the number of observations to signal when the shifts occurs
in the process, this study proposed the Exponentially Weighted Moving Average
(EWMA) median control charts with Variable Sampling Size (VSS). Give the distribution
function of the median value assume that the distribution of observations from
a process is normally distributed. Then using the Markov chain method to establish
a model to calculate the average number of observations to signal (ANOS) of
median control chart. Finally, compare the ANOS of the new model with that of
the conventional fixed sampling size EWMA control chart and VSS EWMA mean control
chart. The data showed that, the designed new model can effectively reduce the
ANOS when the process is out of control. That is to say, the new model effectively
improves the efficiency of the monitoring process, shifts can be discovered
in a shorter period of time which make a great significance to the actual production.]]>Baxley, Jr. R.V.,199527275282Chang, S.Y. and D.S. Bai,200117397406Chou, C.Y., C.H. Chen and H.R. Liu, 200640879896Crowder, S.,198921155162Costa, A.F.B.,199426155163Costa, A.F.B.,199729197204Ji, M., X. Zhao and W. Tang,200624114119 (In Chinese)Prabhu, S.S., G.C. Runger and J.B. Keats,19933128952909Prabhu, S.S., D.C. Montgomery and G.C. Runger,199426164176Reynolds, Jr. M.R. and J.C. Arnold,200133511530Reynolds, Jr. M.R.,199628497510Roberts, S.W.,19591239250Saccucci, M.S. and J.M. Lucas,199022154162Wang, Z.J.,200218316323, (In Chinese)Zhang, W.M.,2000173135, (In Chinese)