Table 1.

Types of study design

Design type	Advantages	Disadvantages
Case series	Suitable for rare diseases or new treatments	No comparison group
		Retrospective nature
Case control	Small sample size	Presence of confounding
	Short duration	Retrospective nature
Cohort studies	Evaluates risk factors	Presence of confounding
	Compares two treatments
	May be prospective
Randomized controlled trials	Prospective in nature	Limited generalizability
	Reduce confounding and bias	Potential for low recruitment and high crossover
		High cost and administrative oversight
Systematic review	Provides summation of available literature	Dependent on quality of individual studies

Adapted from Fisher et al[5].