You must have a heard light bulb jokes, for example:
How many optimists does it take to screw in a light bulb? None, they’re convinced that the power will come back on soon.

So how many people does it take to run a SIEM?
Let me count the ways.

Assuming the SIEM has been installed and configured properly (i.e, in accordance with the desired use cases), a few different skill sets are needed (these can all be the same person but that is quite rare).

SIEM Admin: This person handles the RUN function and will maintain the product in operational state and monitor its up-time. Other duties include deploying updates from the vendor and optimizing system performance. This is usually a fraction of a full time equivalent (FTE). About 4-8 hours/week for the typical EventTracker installation.

Security Analyst: This person handles the WATCH function and uses EventTracker for security monitoring. In the case of an incident, reviews activity reports and investigates alerts. Depending on the extent of the infrastructure being monitored, this can range from a fraction of an FTE to several FTEs. Plan for coverage on weekends and after hours. Incident response may require notification of other admin personnel.

SIEM Expert: This person handles the TUNE function and refines/customizes the SIEM rules/content and creates rules to support new use cases. This function requires the highest skill level, familiarity with the network and expertise with the SIEM product.

Back to the (bad) joke:
Q. So how many people does it take to run a SIEM?
A. None! The vendor said it manages itself!