Table 3

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

	Study Design	Number of Studies Included in this Analysis	Effect Size	Lower Limit	Upper Limit	Higgins I ² Statistic of Heterogeneity	Variance	Standard Error	Number of Patients
Oswestry Disability Index	Prospective study	6	0.9217	0.8644	0.9789	0.0000	0.0009	0.0292	2106
	Randomized prospective study	11	0.9100	0.8398	0.9802	0.0000	0.0013	0.0358	1891
	Retrospective study	83	0.9234	0.9095	0.9373	0.0000	0.0001	0.0071	12,464
	ANOVA Q test random effects with separate estimates of T ²				Sig = 0.925		Total patient samples		16,461
VAS back	Prospective study	3	0.5951	0.3093	0.8809	0.0000	0.0213	0.1458	534
	Randomized prospective study	39	0.8009	0.7412	0.8606	0.0000	0.0009	0.0305	6056
	Retrospective study	5	0.8059	0.7236	0.8882	0.0000	0.0018	0.0420	670
	ANOVA Q test random effects with separate estimates of T ²				Sig = 0.204		Total patient samples		7260
VAS leg	Prospective study	7	0.9318	0.8774	0.9862	0.0000	0.0008	0.0278	2258
	Randomized prospective study	7	0.8834	0.8066	0.9603	0.0000	0.0015	0.0392	1594
	Retrospective study	82	0.9134	0.8980	0.9288	0.0000	0.0001	0.0079	11,701
	ANOVA Q test random effects with separate estimates of T ²				Sig = 0.575		Total patient samples		15,553

ANOVA, analysis of variance; Sig, significance level of 95% CI; VAS, visual analog scale.