Control Charts: are used for determining stability of a process. Important
USL – Upper Specification Limit
LSL – Lower Specification Limit
UCL – Upper Control Limit
LCL – Lower Control Limit
First two are set by customer and last two are normally (+-) 3 Sigma.
Normally used to track repititive activities, sometimes they are also used
cost and schedule variances, volume and frequency of scope changes.
A process is out of control when seven consecutive data points are above or
below the mean.