The words "sample" and "population" mean something very particular to statisticians. A population is the entire collection of entities that a researcher wishes to understand or draw conclusions about. For example, in the second half of the 19th century, Gregor Johann Mendel, the originator of genetics, recorded observations about pea plants. Although he was studying specific plants in a laboratory, his objective was to understand the underlying mechanisms behind heredity in all possible pea plants.

Since populations may be large—or in the case of Mendel's pea plants, infinite—we must study representative samples and draw inferences about the population from them. To distinguish the measurable attributes of our samples from the inaccessible attributes of the population, we use the word statistics to refer to the sample...