Answer:
b) unselected a key measure that represents the central tendency of a group of samples used in conjunction with range.
Step-by-step explanation:
The control chart is a graph used to study how a process changes with 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.
Sample average is defined as a key measure that represents the central tendency of a group of samples used in conjunction with range. While Range is defined as a key measure that represents the variation of a specific sample group, used in conjunction with sample average