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Table 2 Criteria for study validity assessment

From: Management of UK priority invasive alien plants: a systematic review protocol

Question/criterion

Response to question

Type of bias addressed

Yes

Partially

No

Unclear

Did the study consist of both temporal and spatial comparisons?

Before-after-control-impact study

Before-and-after study or controlled study

N/A as study is not eligible for inclusion based on inclusion criteria

Lacking sufficient information to judge

Selection bias

Did the study use randomization?

Study accounts for spatial heterogeneity by using appropriate randomisation of samples

N/A as study was either randomized with respect to the management intervention or not (e.g. random site selection but not random allocation of treatments/controls)

Study does not attempt to randomize sampling

Lacking sufficient information to judge

Selection bias

Did the study avoid confounding factors?

Confounding factors were likely to be minimal as a result of blocking/pairing or stated attempts to match samples

Some confounding factors present, likely to have a moderate impact on outcome

Study was subject to confounding factors that could have a major impact on the outcome

Lacking sufficient information to judge

Selection bias and performance bias

Can the study determine causality?

Experimental study in which comparator samples were selected prior to the management intervention being used

Correlative study in which comparators are selected after the management intervention has already been implemented, thereby limiting the ability of researchers to determine the similarity of comparators prior to management intervention use

N/A—studies with no comparator will be excluded

Lacking sufficient information to judge

Selection bias and performance bias