Table 3

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

Outcome Measure	Type of Surgery	Number of Studies Included in This Analysis (Multiple Study Groups Possible)	Effect Sizes	Lower Limit	Upper Limit	Higgins I ² Statistic of Heterogeneity	Variance	SE	N
Oswestry Disability Index	Endoscopy	29	0.912	0.891	0.943	0%	0.0002	0.0132	4364
	Interspinous process spacer	22	0.798	0.713	0.883	0%	0.0019	0.0435	2098
	ANOVA Q random effects test with separate estimates of T ²				P = 0.001		Total N patients		6462
VAS-back	Endoscopy	14	0.661	0.585	0.734	0%	0.0015	0.0389	1574
	Interspinous process spacer	15	0.784	0.644	0.923	0%	0.0050	0.0711	2098
	ANOVA Q random effects test with separate estimates of T ²				P = 0.187		Total N patients		3672
VAS-leg	Endoscopy	28	0.885	0.852	0.917	0%	0.000	0.017	4292
	Interspinous process spacer	24	0.851	0.767	0.935	0%	0.002	0.043	3598
	ANOVA Q random effects test with separate estimates of T ²				P = 0.427		Total N patients		7890