A meta-analysis combines the data findings from two or more studies allowing researchers to improve the precision not available within smaller individual studies.¹ Studies included in the combined analysis must be similar in design and data type to ensure that overall findings are reliable.¹

• You have found one or more studies conducted using similar study design and that measure similar outcomes
• Several individual studies of a particular intervention have been conducted but none has sufficient power to answer a clinical question. This may be particularly useful if the outcome under consideration is rare.
• Studies have produced conflicting results on the question, likely due to the limited number of occurrences. 

1. Deeks JJ, Higgins JPT, Altman DG, McKenzie JE, Veroniki AA (editors). Analysing data and undertaking meta-analyses [last updated November 2024]. In: Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from www.training.cochrane.org/handbook