[R-meta] residual heterogeneity in meta-regression
Dear Wolfgang Picking up the thread once more...Regarding the many studies included in the meta-regression model (up to 450 studies) I do expect very large Q statistics and cannot aim to explain all heterogeneity through meta-regression. Is there a better way to express heterogeneity in this case? I have read that the tau is a better way, however I am not sure of the interpretation and what I may conclude regarding the model and heterogeneity using tau. Regards, Daniel On Mon, Nov 18, 2019 at 4:27 PM Viechtbauer, Wolfgang (SP) <
wolfgang.viechtbauer at maastrichtuniversity.nl> wrote:
Dear Daniel, Roughly, the QE-test statistic should tend to decrease when R^2 is large. Whether this is strictly true depends on how tau^2 is being estimated. However, the QE-test could very well be significant even if R^2 is large. It simply means that there is still a significant amount of residual heterogeneity left. Best, Wolfgang -----Original Message----- From: Daniel M?nsted Shabanzadeh [mailto:dmshaban at gmail.com] Sent: Thursday, 14 November, 2019 11:09 To: Viechtbauer, Wolfgang (SP); r-sig-meta-analysis at r-project.org Subject: residual heterogeneity in meta-regression Dear Wolfgang I am performing a meta-regression on multiple one-arm non-randomised studies in order to explore the impact of moderators on complications following a surgical intervention. Adding moderators (age catrgory of the patient, surgical technique etc.) increases the R2: Mixed-Effects Model (k = 183; tau^2 estimator: REML) tau^2 (estimated amount of residual heterogeneity): 0.0074 (SE = 0.0010) tau (square root of estimated tau^2 value): 0.0860 I^2 (residual heterogeneity / unaccounted variability): 99.20% H^2 (unaccounted variability / sampling variability): 125.63 R^2 (amount of heterogeneity accounted for): 36.78% Test for Residual Heterogeneity: QE(df = 156) = 4730.2255, p-val < .0001 Test of Moderators (coefficient(s) 2:27): QM(df = 26) = 115.5671, p-val < .0001 However, I am unaware of how to interpretate the rising R2 when QE tests keep on beeing significant. So far I understand that the rising R2 indicates that the heterogeneity is beeing partly explained by moderators, however does QE change in case most heterogeneity is explained by moderators? Regards, Daniel Daniel M?nsted Shabanzadeh MD, PhD Department of Gastroenterology, Surgical Unit Hvidovre Hospital Mobile +45 2546 5251