Definitions for estimating magnitude of effects

Size of effect	Definition
Small/slight	Pain scales: Mean 5 to 10 mm improvement on a 100 mm visual analogue scale (VAS), or equivalent
	Back-specific functional status: Mean 5 to 10 mm improvement on the Oswestry Disability Index (ODI), 1 to 2 points on the Roland-Morris Disability Questionnaire (RDQ), or equivalent
	All outcomes: Standardized mean difference (SMD) 0.2 to 0.5
Moderate	Pain scales: Mean 10 to 20 mm improvement on a 100 mm VAS, or equivalent
	Back-specific functional status: Mean 10 to 20 mm improvement on the ODI, 2 to 5 points on the RDQ, or equivalent
	All outcomes: SMD 0.5 to 0.8
Large/substantial	Pain scales: Mean >20 mm improvement on a 100 mm VAS, or equivalent
	Back-specific functional status: Mean >20 mm improvement on the ODI, >5 points on the RDQ, or equivalent
	All outcomes: SMD >0.8

Graphic 58592 Version 2.0