SPC techniques using M/M/1 queueing model

: In a manufacturing process, no two products can be exact, which
might be due to many factors. These variations need to be monitored and
controlled through the use of statistical process control (SPC). When they are
small, and their effects are barely noticeable, we say the process is ‘in control’.
Otherwise, they lead the process to ‘out of control’. Items enter the system and
wait in a line for measurements; by following a queue discipline. Such a queue
is then characterised according to service time, number of quality inspectors
and waiting space. A good process control will also protect the product in the
sense that the lots produced at permissible levels of quality will have a good
chance to be in control. The objective of this paper is to introduce a control
chart using M/M/1 queueing discipline to study and maintain a process control
in a regular interval.

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