An Analytic Variable Limit np Control Chart


Department of Industrial Engineering,Amirkabir University of Technology


The Shewhart np control chart is often used to monitor the quantity of nonconforming, but
it is slow in detecting small deviations. This paper proposes an efficient approach to monitor the quantity
of nonconforming. The novelty of the paper is utilization of an initial belief to construct an analytic
variable limit np control chart. The proposed method uses all gathered data, sequentially. This approach
is signi cantly faster than some existent e ective approaches in detecting small deviations. These charts
are mainly used for evaluation of the initial setup in the process. The simulated results for the average run
length profiles demonstrate the superiority of the new approach against the standard np chart, binomial
CUSUM, binomial EWMA and moving average approach.