Table 1. Comparison between randomized controlled trials and observational studies.

Aspect	RCTs	Observational studies
Randomization	Yes	No
Risk of selection bias	Low	Can be high
Risk of imbalances in baseline risk factors	Low	High
Cost	++++	++
Complexity	++++	++
Duration	++	++++
Appropriate for evaluating efficacy	++++	++ to +++
Appropriate for evaluating effectiveness	+	++++
Appropriate for identifying adverse events	++ to +++	++++

RCTs: randomized controlled trials.