Sammendrag
Systematic reviews are only as good as the evidence they are based on. It is important, therefore, that users of systematic reviews know how much confidence they can place in the conclusions and recommendations arising from such reviews. In this paper we present an overview of some of the most influential systems for assessing the quality of individual primary studies and for grading the overall strength of a body of evidence. We also present an example of the use of such systems based on a systematic review of empirical studies of agile software development