Post 2: Types of study design

When people read about a health research study, they may not pay attention to how the study was designed. But to understand the quality of the findings, it's important to know a bit about study design. 

According to the widely accepted hierarchy of evidence (refer Figure 1), most of the health research that makes news headlines can be broken down into two basic types: observational and experimental.   

Observational studies involve observing and gathering data on existing phenomenon and, without any interventions or changes, descriptive information on habits, beliefs and outcomes are gathered.  Observational research produces evidence of correlations, which can be used to make predictions¹.  On the other hand, with experimental research, studies can include interventions to find cause and affect relationships, which are generally considered to be more reliable and trustworthy, and allows us to analyse systems and how they interact¹.   

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1 Ho PM Peterson PN Masoudi FA. Key issues in outcomes research. Circulation.    2008;118:1675-1684