Option a: You kill the plant by mistake, your mom finds it, you get busted by the landlord, the cat eats it, it dies of any of an innumerable variety of ailments before harvest...
Yield=nothing.
Option b: You start with incorrect genetics and/or equipment, have a rough but very edumacational first grow, and get a bit of bud.
Yield= some joints and some k-new k-nowledge that ya can't get in college...
Option c: You read a lot before growing and select a strain and grow style appropriate to your skills and space.
Yield= up to 0.5 grams per watt of HPS light per month in flower, or outdoors yield= up to the potential of the specific strain.

The moral of this story is, you get out what you put in.