Table 2.

Proposed scores for assessing the validity of study relevant to small randomised controlled trial under design

Design	Validity score
Randomised controlled trial:
No major flaws	1
Questionable quality	0.8
Major flaws	0.6
Non-randomised trial:
Prospective controlled	0.4
Single arm study:
With prespecified historical controls	0.3
No historical controls	0.2
Case study:
Series	0.1
Single report	0.05