Chapter 8: Gathering Research and Establishing Evidence
The operator AND is used to narrow or focus a search by finding a subset of results containing all of the keywords or search terms. For simplicity, the example depicted by the Venn diagram that follows contains only two key concepts and no synonyms or related terms. On the left, the pinkish-coloured circle labelled graphic novels represents the hits (articles, books etcetera in the database) that contain the words graphic novels. A second, yellowish-coloured circle on the right, represents all of the hits that contain the word teaching. The two sets of searches overlap since a small number of the hits contain both graphic novels AND teaching. This subset is shown in the diagram in the orange portion where the two circles or sets overlap. It is labelled AND because it represents the portion of the hits from the two concepts that contain both the first AND the second concept. The AND operator is the most commonly used Boolean operator.
Example Venn diagram using the AND operator: graphic novels AND teaching
If you decide that you still have too many results when you searched for only two concepts, you can refine your search by adding a third distinct concept. This will narrow your results considerably because it is more precise. The following Venn diagram demonstrates what happens when you modify the search used in the previous example by adding a third keyword: Shakespeare. [Note that most databases allow both upper and lower case when searching for proper names.]
In this example the set of hits dealing with Shakespeare are represented by the blue-coloured circle shown beneath the pinkish circle representing graphic novels and the yellowish circle representing teaching. All three circles overlap to some extent since one, two, or all three keywords may be applied to the same articles, books etcetera in the database. In this example, the small, almost triangular-shaped orange patch labelled AND in the centre of the diagram represents the relatively small subset of hits that contain all three concepts: graphic novels AND teaching AND shakespeare.
Example of a Venn diagram using the AND operator and three distinct concepts: graphic novels AND teaching AND shakespeare