From the process perspective (as depicted in the right graphic of Figure 1), we
think of a population or a sample as resulting from an ongoing, dynamic process, a
process in which the value of each observation is determined by a large number of
causes, some of which we may know and others of which we may not. This view
moves to the foreground questions about why a process operates as it does and what
factors may affect it. In our gun control example, we might imagine people’s
opinions on the issue as being in a state of flux, subject to numerous and complex
influences. We sample from that process to gauge the net effect of those influences
at a point in time, or perhaps to determine whether that process may have changed
over some time period