Quality and Reliability Methods - SAS

Chapter 2 Statistical Control Charts 33
The Control Chart Launch Dialog
The examples shown in Figure 2.7 compare the X -chart for the Coating.jmp data with control lines drawn
with KSigma =3 and KSigma =4.
Figure 2.7 K Sigma =3 (left) and K Sigma=4 (right) Control Limits
Alpha
The Alpha parameter option specifies control limits (also called probability limits) in terms of the probability
α that a single subgroup statistic exceeds its control limits, assuming that the process is in control. To specify
alpha, click the Alpha radio button and enter the probability you want. Reasonable choices for α are 0.01 or
0.001. The Alpha value equivalent to a KSigma of 3 is 0.0027.
Using Specified Statistics
After specifying a process variable, if you click the Specify Stats (when available) button on the Control
Chart Launch dialog, a tab with editable fields is appended to the bottom of the launch dialog. This lets you
enter historical statistics (statistics obtained from historical data) for the process variable. The Control Chart
platform uses those entries to construct control charts. The example here shows 1 as the standard deviation
of the process variable and 20 as the mean measurement.
Figure 2.8 Example of Specify Stats
Note: When the mean is user-specified, it is labeled in the plot as μ0.