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Table 3 Classification of study quality (Source: [44])

From: Does land abandonment decrease species richness and abundance of plants and animals in Mediterranean pastures, arable lands and permanent croplands?

Category Quality of evidence
I Strong evidence obtained from at least one properly designed; randomised controlled trial of appropriate size.
II-1 Evidence from well designed controlled trials without randomisation.
II-2 Evidence from a comparison of differences between sites with and without (controls) a desired species or community.
II-3 Evidence obtained from multiple time series or from dramatic results in uncontrolled experiments.
III Opinions of respected authorities based on qualitative field evidence, descriptive studies or reports of expert committees.
IV Evidence inadequate owing to problems of methodology e.g. sample size, length or comprehensiveness of monitoring or, conflicts of evidence.