Here are some strategies for quickly and accurately broadening, narrowing, or refining your search results. Most online indexes and databases have at least some of these options, but there are often differences in how to use them, so read the help screens for the database you are using. Many of these techniques are demonstrated in this video on Getting the most out of OneSearch.
Precision and Recall
But first, a little searching theory, to see how these techniques can be useful. When you search an online database, you want to find as much relevant information in the database as you can while avoiding getting irrelevant items along with your results.
Precision – how much of the information your search retrieved is actually relevant to your needs. If your search retrieves a lot of irrelevant results, you can use some of the techniques below to make a more precise search.
Recall – how much of the relevant information in the database you were able to find with your search. This is much more difficult to determine: you don't know how much useful information your search didn't find. By using some of the techniques below to increase recall, you can be more confident you have found at least most of the useful information in the database.
Increase precision by being very specific and narrow in your search, which will give you few if any irrelevant results, but that risks missing some useful information. Increase recall by broadening your search and thus finding more useful information, but that tends to increase the "noise" (irrelevant results) in your results.
If you need just a few good results, focus on increasing precision: it doesn't matter if you don't find everything relevant, and you don't want to wade through lots of irrelevant results. But for a full literature review for a big research project, you need to find as many relevant articles as you can, so focus on increasing recall even if you have to sort out a lot of irrelevant results.
Keyword vs. Subject Searching
Keyword – searches everywhere in a source: title, author, abstract, full text, etc. Retrieves all sources which have that term anywhere in any context, but does not find synonyms of the term. Usually finds more results, but also more irrelevant results.
Subject – searches subject tags selected from a database’s list of standardized subject headings. Retrieves only sources tagged with that subject heading, but includes sources in which the author used synonyms other than the actual subject heading. Usually finds fewer results, but more of the results are relevant.
Start with keywords: think of different terms and phrases to describe your topic and search for them. Pick the best results and see what subject headings are tagged to them, then use those subject terms to find more sources like them.
Searching for ‘Shakespeare’ as a keyword (“any field”) will find results where Shakespeare is the author, a major subject, or briefly mentioned. Searching for ‘Shakespeare’ as a subject finds only results where Shakespeare is a major subject.
Searching for ‘elderly’ as a keyword will find results with that term anywhere at least once and in any context (e.g. elderly trees), but will not find results that talk about ‘senior citizens’, ‘aged’, ‘geriatric’, or other synonyms. Searching ‘elderly’ as a subject (if it is a subject heading) will find results where elderly people are a main subject regardless of what synonyms the author used.
Broader / Narrower / Related Terms
If you do not find enough information on your topic, think of synonyms or other ways of stating your topic and do another search. Or, use more general terms to broaden your search.
If you find too much information on your topic, add more terms or use more specific terms to narrow your search, or use synonyms or related terms to refocus your search.
Databases that use subject headings often include a thesaurus of broader, narrower, and related terms for their subject headings, along with what they mean by the term and what synonyms it includes.
Use AND, OR, and NOT search operators to combine two or more terms. This allows you to define a complex set of search criteria in a single search.
AND - Finds records in the database with all of your search terms; i.e., AND narrows a search and makes it more specific, finding sources which are about both of two different topics.
Find only those records in the database which include both terms 'dogs' and 'cats' somewhere in the record.
OR - Finds records in the database with at least one of your search terms; i.e., OR broadens a search, finding sources which include one or the other (or both) of two different terms.
Find all records in the database which are about either dogs or cats, including those sources which are about both dogs and cats.
NOT - Excludes records which have a specified search term from your results; i.e. NOT narrows a search, eliminating a subset of sources from a larger set.
Find sources on anything about dogs except for things also about cats.
Complex searches - You can make very complex searches by using more than one operator in a search:
Find sources about food for pets other than cats and dogs.
Broaden a search by searching for variant endings of a word.
For example, to search for computers, computerization, etc., type "comput*". You will retrieve everything in the database on computers, computing, computerize, computerization, etc. Some databases also have "wildcard" symbols, to search for variant spellings within a word. For example, "lab*r" would find 'labor' and 'labour'.
Note: Different databases use different keys for truncation and wildcards (usually * or $ or ?) so check the help guide for each database you use.
Use quotes around a string of words to search them as a phrase rather than as separate keywords.
The terms ‘population’ and ‘fund’ are likely to show up somewhere in other documents about the United Nations; using quotes will narrow your results to only those documents about the United Nations Population Fund specifically.
Phrase searching is also useful when your phrase contains "stop words," common words such as 'a', 'an', 'the', 'of', etc, which are usually ignored by search tools. By using a phrase search, you can search for the entire phrase, stop words included:
Narrow your search by specifying just one type of source to find, e.g. books, articles, images, sound recordings ...
Another common option is to limit your search to find only peer reviewed articles, i.e. articles in academic journals which are reviewed by other scholars and researchers in the field before they are published to check for accuracy and importance of contents.
Specify that two or more terms must appear close to one another, e.g. "adjacent" to each other (in any order), "within" the same sentence or paragraph, or "near" (e.g. within 5 words of) each other. This is especially useful for searching full text databases.
This search limits results to articles with 'diabetes' and 'children' within 5 words of each other:
Specific commands for proximity searching vary between databases, so consult each database's help screens.