The probability density function is a statistical measurement of how often investment returns fall within a specified range. PDFs are typically depicted on a graph, with a normal bell curve ...

population-density graph. The map is the creation of University of Oregon graduate student Derek Watkins, whose entire Web site—particularly the posts about post offices—is worth checking out.

This line is the most populated thing on the chart because ... Other constant-density lines correspond to other condensation events—bosons and protons, for example. They are more sparsely ...