Quality manager technical interview questions often revolve around understanding tools, techniques and processes – one such tool is the control chart which is basically a quality control analysis tool used to understand and analyze how a process changes over time; it is one of the several graphical tools that quality control analysis uses. It is also called a statistical process chart or SPC chart and it helps gauge causes of variations as well as process improvements made from time to time. Control charts are instrumental in process improvement and tracking those improvements. A control chart has 3 essential elements:  Visual time series graph - to show data points at defined intervals  Horizontal control line - to visualize trends and variations  Upper and Lower control limits - limits above and below the control line defining the thresholds  Control charts help QA understand the trends, and problem areas and focus efforts towards these alongside filling gaps in the process loopholes. They thereby help minimize the risk that teams would otherwise encounter and spend resources fixing.