In the preceding description, we spoke of processes rather than populations. We
contrast these two ways of thinking about samples or batches of data, as shown in
Figure 1. When we think of a sample as a subset of a population (see the left
graphic), we see the sample as a piece allowing us to guess at the whole: The
average and shape of the sample allow us perhaps to estimate the average and shape
of the population. If we wanted to estimate the percentage of the U.S. population
favoring gun control, we would imagine there being a population percentage of
some unknown value, and our goal would be to estimate that percentage from a
well-chosen sample. Thinking in these terms, we tend to view the population as
static and to push to the background questions about why the population might be
the way it is or how it might be changing.