Ongoing Process Capability
Ongoing Process Capability is a long term measure of statistical process control or process performance. It differs from preliminary process capability by utilizing data from a longer time period so as to include all common causes of variation, in particular, those common causes that may result in process shifts affecting a number of sample intervals. Systematic or repetitive patterns of special cause may also be included if the underlying reasons for these special causes are understood. The time required for ongoing capability evaluation depend on the time required for the sources of variation to vary throughout their full ranges, but will typically be three to six months. (also machine capability)