Inbiostatistics,strength of evidence is the strength of a conductedstudy that can be assessed inhealth care interventions, e.g. to identify effective health care programs and evaluate the quality of the research in health care. It can be graded with differentdescriptive oranalytical statistical methods.[1][2]Hierarchy of study design, for example using acase-study,ecological study,cross-sectional,case-control,cohort, orexperimental, although not always in this order is a general rule to a high "strength of evidence" of a clinical study.[3][4][5]