Table 2 Draft quality coding tool

Generic data quality features

Specific data quality features

Quality element

Quality score

Internal validity of study

N/A

Clear aims

2

Treatment and control groups similar at start of trial (low heterogeneity between locations, size of exp. areas, soil type, shading, plant types etc.)

2

Outcomes measured accurately and reliably

2

Control of confounding variables

2

Replications of study

2

Study Design

N/A

Randomised block design time series (pre-intervention data/observations)

80

Non-randomised block design time series

60

Historical dataset e.g. >10 years (not from current experimental observation)

50

Data without comparator

30

Descriptive, field observations

20

Expert opinion

10

Measurement of outcomes

Quantitative measurements of intervention

Population size, range, density, fecundity–pop. counts/mark-recapture/nest counts/dropping counts

10

Qualitative/descriptive observations of intervention (e.g. vague estimate of time since introduction)

Population size, range, density, fecundity

5