Graph which plots series of successive observations of specific procedure, operation or step at regular time intervals is called

Graph which plots series of successive observations of specific procedure, operation or step at regular time intervals is called control chart. The control chart is a graph used to study how a process changes over time. Data are plotted in time order. A control chart always has a central line for the average, an upper line for the upper control limit, and a lower line for the lower control limit. These lines are determined from historical data.