Definition and explanation
Adequacy of data is an overall determination of the degree of richness and quantity of data supporting a review finding.
In assessing adequacy of data, we define "rich data" as data that provide us with sufficient detail to gain an understanding of the phenomenon we are studying-for instance, an understanding of participants' perceptions and experiences of a given topic. In contrast, thin data do not provide enough detail to develop an understanding of the phenomenon of interest.
In addition to data richness, quantity of data is also important. When a review finding is supported by data from only one or few primary studies, participants, or observations, we are less confident that the review finding reflects the phenomenon of interest. This is because when only a few studies or only small studies exist or when few are sampled, we do not know whether studies undertaken in other settings or groups would have reported similar findings.