Optimal design of synthetic np control chart based on median run length

ABSTRACT

The synthetic np chart is a combination of the np sub-chart and the conforming run length sub-chart. A procedure for the optimal design of the synthetic np chart is provided by minimizing the out-of-control median run length (MRL). The comparative results show that the synthetic np chart performs better than the corresponding standard np chart for detecting process shifts in the fraction non conforming, in terms of the MRL. An example is given to illustrate the operation of the synthetic np chart.

KEYWORDS:

• Median run length
• np chart
• percentage point of the run length
• synthetic chart.