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Making Searching More Precise With Boolean Operators

Boolean searching allows you to research a topic with greater precision by linking the essential elements of your research question with the operators and, or, or not. In this way you can broaden or narrow a search. 

And narrows a search because it asks that all sources in the results list have each search term (two or more) in them. So if you were to add and medical to a search for marijuana, or hashish, or cannabis, you would limit your sources to those with marijuana and medical, or hashish and medical, or cannabis and medical.

Here's an example of the way and would narrow this search.

Suppose that the database has 90 documents with the term medical in them. If you join medical to the other three terms with and, you will get a maximum of 90 hits (sources in your results list) and most likely many fewer since every document must have medical and one of the other three terms in it. Your results might be something like this.

medical and marijuana 22 documents
medical and cannabis 6 documents
medical and hashish 3 documents

Your results list would have no more than 31 documents.

Not allows you to narrow a search further by eliminating what would be irrelevant hits. For example, for a paper on legalizing marijuana, you can specify not Canada thereby eliminating any articles on legalizing marijuana in Canada.  

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