Different zones in the control chart Now, first of all, we define the zone for understanding the Control Chart Rules. Please show the below picture for a clear understanding of UCL, LCL, Centreline and different Zone A, Zone B, and Zone C. For example, charts for multiple locations within the subgroup are utilized when a subgroup consists of measurements that may come from different distributions. Examples include: – Multiple measurements on the same unit (e.g. diameter in 3 places) – Units produced during the same cycle from different cavities, machining locations, filling heads, etc. April 2004 In this issue "In Control" Control Chart Points Beyond the Control Limits Zone Tests: Setting the Zones and Zone A Zone Tests: Zones B and C Test for Stratification Test for Mixtures Rule of Seven Tests Quick Links The focus for this month is on interpreting control charts. Processes, whether manufacturing or service in nature, are variable. You will not always get the same result