My Reading on ASQ CQA HB Part I-IA~IE-s

Part IB
The Shewhart control chart has a baseline and upper and lower limits, shown as dashed lines,
that are symmetric about the baseline. Measurements are plotted on the chart versus a time line.
Measurements that are outside the limits are considered to be out of control.
The baseline for the control chart is the
accepted value, an average of the
historical check standard values. A
minimum of 100 check standard values is
required to establish an accepted value.
The upper (UCL) and lower (LCL) control
limits are:
UCL = Accepted value + k*process
standard deviation
LCL = Accepted value - k*process
standard deviation
where the process standard deviation is
the standard deviation computed from the
check standard database.
18 March 1891 – 11March 1967
https://www.itl.nist.gov/div898/handbook/mpc/section2/mpc221.htm
Charlie Chong/ Fion Zhang