Not all evidence is created equal.

Evi­dence is strong when we have con­fi­dence that addi­tion­al data will not reverse our con­clu­sions. This is gen­er­al­ly the case where there are con­sis­tent find­ings across mul­ti­ple stud­ies or where the mag­ni­tude of effects are very large. Stud­ies where rig­or­ous exper­i­men­tal designs are used (includ­ing before-com­par­isons as well as an appro­pri­ate con­trol group) also gen­er­ate con­fi­dence. Although there is not yet con­sen­sus among con­ser­va­tion prac­ti­tion­ers around a par­tic­u­lar for­mu­la for evi­dence grad­ing at this time, expert judg­ment should con­sid­er these fac­tors when assess­ing strength of evidence.