Public Health

Library of the Health Sciences

Planning your research saves you time.

There are two steps you can take to plan your research before actually going to a database that will

  • save you time and
  • help you figure out what you should be typing into that database's search bar.

Step one - the clinical question:

State your research idea as a clinical question, which should be specific and answerable:

example: How effective is the use of mouth guards in reducing mild traumatic brain injury incidence in high school athletes?


Step two - PICO:

Check that your question is indeed a "clinical question" by checking to see that it contains three or four specific variables known as PICO:

  • a Population/Problem,
  • an Intervention,
  • a Comparison (not always necessary),
  • and an Outcome

here is the same clinical question in PICO format:

P "high school athletes" AND "traumatic brain injury"
I "mouth guard"
C n/a
O reduction

You will notice that the Population box above has two variables with an all-caps AND connecting them. This is a Boolean command phrase, and will tell the database that both terms are required.


Step three: turn your PICO into a database search phrase

Charting your question as a PICO gives you pieces of the search phrase you need to search on a database. All you need to do now is combine the pieces correctly, using Boolean commands AND, OR, and NOT


Planning the Search

There are several worksheets available directed at planning your search.  Here is one example and a guide for thinking through the PICO process.

Types of Questions

Diagnostic Tests – how to select and interpret diagnostic, in order to confirm or exclude a diagnosis, based on considering their precision, accuracy, acceptability, safety, expense, etc.
Harm/Etiology – how to identify causes or risk factors for disease.
Prognosis – how to estimate patient’s likely clinical course over time and anticipate likely complications of the disorder.
Therapy – how to select treatments to offer patients that do more good than harm and that are worth the efforts and costs of using them.
From Straus SE, Richardson WS, Glasziou P, Haynes RB. Evidence-based medicine: How to practice and teach EBM. 3. ed., repr. ed. Edinburgh [u.a.]: Elsevier/Churchill Livingstone; 2008.

Levels of Evidence

There are several levels of evidence, all related to the types of research and publications.  Many evidence based resources incorporate evidence that ranges from the very highest level to the very basic level.