Standard Deviation Summary in Monte Carlo Simulations Across Multiple Corners

The tool versions are below:

Virtuoso IC 6.1.8-64b.500.33
Spectre 23.1.0.063 64bit

Hello,

When performing a Monte Carlo simulation, the Yield tab shows a standard deviation in the results.

If the simulation is performed with several corners (not parameters), the question is which standard deviation value is used for the summary output. Each corner has its own standard deviation.

Is the worst-case standard deviation used for the summary? If so, why is it sometimes the larger and sometimes the smaller value?

At 100% yield it seems to always be the larger value (worst case), but at 0% yield it is sometimes the larger and sometimes the smaller value.

Does anyone know how this value is determined?

Thanks very much for your reply!

Alexander