For any given velocity distribution, you have a y-axis with probability and an x-axis of velocity. Without really thinking much about it, I had assumed the normalisation condition was that the area under the graph (the integral of the function w.r.t. velocity) would be equal to 1. Of course, the area under the graph has the dimensions of velocity and so it doesn't make sense to set the area to 1. So my question is, what IS the normalisation condition for a velocity distribution??