Theory of Control Charts DCOVA A process is the value added transformation of inputs to outputs Control Charts are used to monitor variation in a measured value from a process Inherent variation refers to process variation that exists naturally.This variation can be reduced but not eliminated Statistics for Managers Using Microsoft Excel Statistics for Managers Using Microsoft Excel Theory of Control Charts  A process is the value added transformation of inputs to outputs  Control Charts are used to monitor variation in a measured value from a process  Inherent variation refers to process variation that exists naturally. This variation can be reduced but not eliminated DCOVA