Table 1 Design specifications of the economic statistical model.
From: Economic statistical model of the np chart for monitoring defectives
Process specifications | \({p}_{0}\) | In-control fraction nonconforming. It is calculated from the historical data examined during in-control process |
Ď„ | Minimum allowable in-control \({ATS}_{0}\). It is selected depending on the false alarm rate specifications | |
r | Inspection rate. It is estimated based on the accessibility of resources like workforce and equipment | |
\({\delta }_{max}\) | Maximum shift in fraction nonconforming. It is decided based on the maximum shift that the user wishes to detect | |
ε | Assignable cause rate of occurrence | |
e | Time to estimate observed data of a sample. It can be easily estimated from a field test | |
D | Time between detecting the out-of-control condition and removing the assignable cause | |
Cost specifications | b | Sampling fixed cost |
c | Sampling variable cost | |
W | Cost of locating and resolving an assignable cause | |
T | False alarm examining cost | |
M | Cost incurred due to the increasing p shift |
