Abstract:
The objective of this research is to find the explicit formula of Double Moving Average control chart (DMA Chart) by Probability Theory when observations are from normal and exponential distributions. The performance of DMA Chart, Shewhart x ̅ Chart, Moving Average control chart (MA Chart) and Exponentially Weighted Moving Average control chart (EWMA Chart) for various magnitude of changes are compared. Furthermore, the explicit formula can be obtained an optimal parameter (w,H) for designing of DMA Chart. The performance of control chart is characterized by the Average Run Length (ARL). The accuracy of numerical results obtained from explicit formula is compared with the results obtained from Monte Carlo Simulation (MC) which they are in good agreement. The results found that the performance of EWMA is superior to Shewhart x ̅, MA and DMA Charts for small shift ( δ ≤.01), the DMA chart performs better than Shewhart x ̅, MA and EWMA Charts for moderate shifts (0.2 ≤ δ≤1.5). For large shift ( δ >1.5) the performance of the Shewhart x ̅, MA and DMA Charts are not significantly different.