Table 3 Study bias assessment categories
Risk of Bias | High | Low | |
|---|---|---|---|
General Bias Based on Bilotta et al. [44] | Selection bias (Inadequate randomisation) | No randomisation (site /tree selection based on availability, expert judgement or results) | Randomisation (site /tree selection based on random number generator/tossing a coin) |
Performance and detection bias (researcher bias) | No blinding / Blinding broken / insufficient information | Blinding done | |
Reporting bias (incomplete results (variables)) | Not all pre-specified outcomes reported; measurements/methods for some outcomes were not pre-specified; incomplete reporting of one or more outcomes; not reporting on an expected outcome | Study protocol is available and pre-specified outcomes are reported on; study protocol not available but all expected outcomes are reported on | |
Attrition bias (incomplete results (observations)) | Resulting data points lower than expected from the methodology; No reason given for missing data related to outcome; bad imputation | Reported data points correspond to methodology; data omission or imputation well documented and justified | |
Adapted criteria | External validity [45] | Spatial replication (Experimental units) 2 field (widespread application) Or 2 rows (row-based installation) Or 2 trees (targeted application) OR Temporal replication 1 frost night (temperature change) 1 year (yield/damage) Observations (assessment level) per experimental unit < 4 trees (widespread or row-based) < 4 branches (targeted application) | > 2 fields > 2rows > 2 trees > 1 frost nights > 1 years > = 4 trees > = 4 branches |
Baseline of test and control groups compared | At least one of the following differs or is not described: management (pruning), soil type, topographic position, differences in cultivar and/or rootstock, orchard age | All of the following factors are comparable: management (pruning), soil type, topographic position, differences in cultivar and/or rootstock, orchard age | |
Location of temperature sensor given | Closest meteorological station > 10 km away; no detail given | Local sensors on field and beside flowers at several tree heights (lower, middle and upper position in tree) | |
Reporting method | Mean effects per experiment only | Raw data, Measure of variation |