Table 3 Critical appraisal criteria
Factor | Low risk of bias | Moderate risk of bias | High risk of bias |
|---|---|---|---|
Study design | Experimental studies (treatment vs control) | Quasi-experimental studies (including concurrent controls) | Case studies and observational studies |
Objectives/hypothesis | Clear relation between objectives and methodology | Clear relation between objectives and methodology | No relation between objectives and methodology |
Sampling | Sampling method is suitable for gathering data on the population of interest | The method used for sampling is appropriate for data gathering on population of interest | Sampling method is not suitable for the population of interest |
Replicates are proper (interventions are replicated) | Replicates are proper | ||
Intervention and comparator areas are well-matched (soil conditions are the same) | Intervention and comparator areas are well-matched (soil conditions do not differ profoundly) | ||
Confounding factors not present (both intervention and comparator sites are treated equally) | Confounding factors not present (both intervention and comparator sites are treated equally) | ||
Consideration of heterogeneity/effect modifiers | Precisely determined/considered effect modifiers | Effect modifiers are considered | Effect modifiers not considered or determined |
Statistical analysis | Clear description of statistical analysis and results | Statistical analysis and results are clear enough | Not appropriate statistical analysis and results |