See the excerpt below, from the JMP Help select Scripting Index > Objects > search for nonconformance then press the Topic Help button.
Overall Sigma will be larger than Within Sigma, and % out of spec will be larger. If your data is representative of the full population and can be modeled as a normal distribution and your specified control chart subgrouping, then yes 16 out of 1000.
JMP Help:
The Individual Details report for a variable with a normal distribution shows a histogram, process summary details, and capability and
nonconformance statistics. The histogram shows the distribution of the values, the lower and upper specification limits and the process target (if they are specified), and one or two curves showing the assumed distribution. The histogram in
Figure 11.14 shows two normal curves, one based on the overall estimate of standard deviation and the other based on the within-subgroup estimate.
When you fit your process with a normal distribution, the Process Summary includes the Stability Index, which is a measure of stability of the process. The stability index is defined as follows:
(Overall Sigma/Within Sigma)
If Calculate Between-and-Within Capability is specified for a process in the launch window, the stability index for that process is defined as follows:
(Overall Sigma/Between-and-Within Sigma)
A stable process has stability index near one. Higher values indicate less stability.
Note: You can change the preferences for stability assessment type in File > Preferences > Platforms > Process Capability. This changes the stability assessment type used through the Process Capability platform.
