Hello Everyone,
I found the following definition of Control limits in the PMBOK glossary.
"The area composed of three standard deviations on either side of the centerline, or mean, of a normal distribution of data plotted on a control chart that reflects the expected variation in the data."
What does the three standard deviations denote? The two control limits UCL and LCL are shown in the control chart diagram. What is the third SD mentioned here?