Originally Posted by feonateresa
I thought MSU was 18 actually. Why do they differ from the university? I assume that the university's number is more, erm, important than the MSU as a whole.
There's a few reasons why the MSU would have a lower unit requirement than the University for membership purposes.
The MSU represents full-time students only. Part-time students are represented my MAPS (McMaster Association of Part-Time Students). The 18 unit definition comes from an agreement between these two bodies.
Having a lower unit requirement for MSU membership does a few things: it allows more students to run for office or otherwise participate in the MSU; it provides more income for the MSU via membership fees; it provides its services to more students; and those are just the few that I could think of off the top of my head.
The 24 unit definition by the University is actually relatively unimportant except for the situation where you might be applying to a grad school that requires your last undergraduate year to be full-time.