In the text the word sample is used in two ways. The sample referred to in Part 1 is the portion of material submitted for chemical analysis, e.g. a 10 mL sample of olive oil removed from a one litre bottle of oil for the purpose of chemical analysis. When statistical procedures are applied to the results of analytical measurements (Part 6) the term sample refers to the segment of all the possible results, i.e. the population that is being used to calculate the statistic. Ten measurements are used to calculate the sample standard deviation (see random errors, Section 6.2); the ten results are only a portion of the infinite number of possible measurements.

Terms used in describing samples and sampling procedures are many and varied. The text below aims to describe those in common usage. It is clear that there is potential for confusion. It should therefore be a golden rule for any analytical chemist to define clearly the terms used in the context of the particular problem being addressed so that any procedure can be understood and repeated. ^{[1] [2] [3]}