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Systematic Reviews

This is a guide to conducting systematic reviews, a structured, comprehensive approach to reviewing the literature on a selected topic.


The first step in the systematic review process is to choose an appropriate research question. It's important to create a clear and unambiguous research question with sharply defined parameters, because this will determine the inclusion and exclusion criteria for your review. The most common approach is to use what's called the PICO Model. 

P: Population/Patient

I: Intervention

C: Comparison (optional)

O: Outcome

  • Here's an example: In homeless, intravenous drug-users (population) do needle exchange programs (intervention) lead to reduced levels of HIV incidence compared to a control group (comparison)?

This model was developed for work with medical research and is most appropriate for evaluating quantitative studies. There are alternative methods that may be more appropriate for other disciplines and qualitative studies.

Alternative Models

For qualitative studies, researchers sometimes use the similarly named PICo Model.

P: Population

I: Phenomenon of Interest

Co: Context

  • Example: How do middle-school students from low-income homes (population) experience bullying (phenomenon of interest) in public schools (context)

The SPIDER Model is another approach to formulating a research question that takes into account study type and design.

S: Sample

PI: Phenomenon of Interest

D: Design

E: Evaluation

R: Research Type


  • Do spouses of military members killed in action (sample) experience benefits (evaluation) from support groups (pheomenon of interest)
  • Design: Interview, survey, questionairre
  • Research Type: Qualitative