Table 4

Analysis of effect size, heterogeneity, and ANOVA testing of difference by surgery indication.

Outcome Measure	Indication for Surgery	Number of Studies Included in This Analysis (Multiple Study Groups Possible)	Effect Size	Lower Limit	Upper Limit	Higgins I ² Statistic of Heterogeneity	Variance	SE	N
Oswestry Disability Index	HNP radiculopathy	8	0.920	0.862	0.977	0%	0.0009	0.0295	880
	Stenosis claudication	21	0.815	0.722	0.907	0%	0.0022	0.0472	2004
	ANOVA Q random effects test with separate estimates of T ²				P = 0.076		Total N patients		2884
VAS-back	HNP radiculopathy	4	0.532	0.271	0.794	<1%	0.0178	0.1333	506
	Stenosis claudication	14	0.694	0.514	0.874	0%	0.0084	0.0919	2780
	ANOVA Q random effects test with separate estimates of T ²				P = 0.307		Total N patients		3286
VAS-leg	HNP radiculopathy	8	0.868	0.769	0.966	0%	0.0025	0.0503	880
	Stenosis claudication	23	0.830	0.736	0.924	0%	0.0023	0.0480	3584
	ANOVA Q random effects test with separate estimates of T ²				P = 0.869		Total N patients		4464

ANOVA, analysis of variance; HNP, herniated nucleus pulposus; VAS, visual analog scale.