Use Cases

Comparative Effectiveness Research

Understanding controlled trials: Why are randomised controlled trials important?


Sibbald, B. and M. Roland


Randomised controlled trials are the most rigorous way of determining whether a cause-effect relation exists between treatment and outcome and for assessing the cost effectiveness of a treatment. They have several important features:
-Random allocation to intervention groups

-Patients and trialists should remain unaware of which treatment was given until the study is completed-although such double blind studies are not always feasible or appropriate

-All intervention groups are treated identically except for the experimental treatment

-Patients are normally analysed within the group to which they were allocated, irrespective of whether they experienced the intended intervention (intention to treat analysis)

-The analysis is focused on estimating the size of the difference in predefined outcomes between intervention groups.

Other study designs, including non-randomised controlled...



Sibbald, B. and M. Roland (1998). "Understanding controlled trials: Why are randomised controlled trials important?" Bmj 316(7126): 201.

Website: http://www.bmj.com/content/316/7126/201