Table 2.

Study design and the potential level of evidence

Study type	Designs with the potential to provide strong evidence	Designs with the potential to provide reasonable evidence	Designs likely to provide weak or misleading evidence
CRT	CRT that is blinded to participants and investigators OR uses an objective outcome measure	CRT that is not blinded to the participants AND uses a subjective outcome measure AND study participation is not obvious to participants (see text)	CRT that is not blinded to the participants AND uses a subjective outcome measure AND study participation is obvious to participants (see text)
NCT	NCT with very good balance of the outcome of interest at baseline across arms NCT conducted as controlled interrupted time series analysis	NCT with imbalance of the outcome of interest at baseline across arms AND no major trend in the control arm	NCT with imbalance of the outcome of interest at baseline across arms AND a major trend in the control arm NCT without baseline measure of the outcome of interest
CBA		CBA with reasonable balance of the outcome of interest at baseline across arms AND no major trend in the control arm CBA with only one cluster per arm AND multiple outcome measures before and after the intervention	CBA with imbalance of the outcome of interest at baseline across arms OR major trend in the control arm CBA with only one cluster per arm AND single outcome measure before and after the intervention
BA		BA with multiple outcome measures before and after the intervention BA with adopter/non-adopter comparison before and after the intervention BA conducted as interrupted time series analysis	BA with a single outcome measure before and after the intervention BA using post-intervention adopter/non-adopter comparison without baseline