Quote from sonoma:
Standard deviation.
Lots of folks here hedge day-in and day-out, so the technical answer to your query isn't so hard. Importantly, they'll want to know what you're trying to accomplish. For instance, are you looking to be protected intraday? The "flash crash" measured on an intraday scale was huge. Double-digit sigma. But viewed over a longer time scale, the decline was not so dramatic, so maybe a different type of hedge would be a better choice. Also tell us whether you're trying to hedge systemic risk or individual equity risk. That will help others point you in the right direction.
I guess it would be a sigma move then. With an income strategy you profit when markets are flat or atleast within a standard deviation. Have any ideas?