Ask HN: Difference between an Accelerator and a University?

Principally, how is an accelerator (like YC), as an institution, any different than universities? which just capitalizes on the selection bias. What is the net value added of the "education"? OR is it just a signaling factor and access to the alumni network. Considering the slim chances of success with any startup, do these add-ons really make a difference for the majority of startups?