Boolean Operators
AND - OR - NOT
Putting the Search Together
AND
Use AND to join the different ideas in your topic together and get articles that talk about both topics:
stroke AND rehabilitation
OR
Use OR to join synonyms or word variations together to get all of the articles that use any of those words:
rehabilitation OR recovery of function
AND - OR Together
When you want to search using both AND and OR, put parentheses around the OR statement:
stroke AND (rehabilitation OR recovery of function)
When you search with keywords, you are trying to find words that authors have used in their titles and abstracts or somehow otherwise appear in the article's entry in a database. Therefore you need to brainstorm all of the possible ways authors could refer to your concept:
"endurance" OR "physical fitness"
"education" OR "training" OR "school" OR "learning"
You can also search using subject headings. Subject headings are keywords assigned by the databases to describe the concepts in an article and to try to take some of the guesswork out of the job of coming up with keywords. Try searching with subject headings and see how your results differ from searching with just keywords.
Still unsure about subject headings? Watch this video for another explanation as well as tips on how to find them.
PICO Questions and Search Strategies
Think of a search strategy as a shopping list for evidence. When you're looking for evidence, there is probably specific types of evidence fitting specific criteria that you need. Planning your strategy in advance can save you some time and keep you organized. Furthermore, having a record of what, where and how you searched can help you replicate your search later or make modifications to improve your results.
Before you start a topic search for a literature review or other assignment, ask yourself these questions:
Placing your research question in the PICO(T) format can help you ensure that your question is answerable. If your question doesn't fit PICO(T), it might be too specific (not enough results) or too general (too many results) to research using the databases. The video tutorial below will take you through the process of developing a PICO(T) question.
This PICO(T) Templates worksheet can also help.
A PICO(T) question also makes searching easier because the type of question determines what type of evidence you should look for:
| Type of PICO(T) Question | Type of Evidence Needed to Answer |
| Diagnosis | Studies reporting performance characteristics |
| Therapy | Clinical trials Randomized Controlled Trials Systematic Reviews (of Clinical Trials and RCTs) |
| Etiology | Cohort Studies Case Control Studies Systematic reviews (of Cohort and Case Control Studies) |
| Prognosis | Cohort Studies |
| Meaning | Qualitative Studies: Ethnography, Phenomenology, Grounded theory, Focus groups |
Remember that some types of evidence are stronger than others. Often evidence is shown in a pyramid, in which each ascending level represents a different type of study design and corresponds to increasing rigor, quality, and reliability of the evidence. In other words, as we ascend through these different study designs, we become more confident that their results are accurate, have less chance of statistical error, and minimize bias from confounding variables that could have influenced the results. (http://www.students4bestevidence.net/the-evidence-based-medicine-pyramid/)
Always aim for the highest level of evidence appropriate to your question type. For your DNS 820 lit review, you will probably be asked to use original research studies only and not systematic reviews. However, if you find a systematic review that answers your question, you can use it to lead you to original research studies relevant to your question.
Modifying an Unsuccessful Search
If you aren't happy with the list of articles your search brings back, here are some ways you might think about changing your search.
1. Too many articles / Articles aren't on topic
2. Too few articles
Photo by Anant Nath Sharma, used with permission under a Creative Commons license
