[R] Metafor -can't calculate heterogeneity with non-positive sampling variances
b.owen11 at imperial.ac.uk
Wed Aug 27 13:48:07 CEST 2014
Hi, I'm doing a meta-analysis in metafor. All is fine except when there are 0s in the values that i'm pooling, then i get a pooled estimate but not the I2 that i am also interested in.
(where yi are the study outcomes, one of which is 0, and vi is the variance of the study outcomes)
Random-Effects Model (k = 17; tau^2 estimator: ML)
logLik deviance AIC BIC AICc
13.0539 Inf -22.1077 -20.4413 -21.2506
tau^2 (estimated amount of total heterogeneity): 0.0119 (SE = 0.0043)
tau (square root of estimated tau^2 value): 0.1089
estimate se zval pval ci.lb ci.ub
0.1837 0.0274 6.7154 <.0001 0.1301 0.2374 ***
Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
1: In rma(yi, vi, data = mix, method = "ML", knha = F, weighted = F, :
There are outcomes with non-positive sampling variances.
2: In rma(yi, vi, data = mix, method = "ML", knha = F, weighted = F, :
Cannot compute Q-test, I^2, or H^2 with non-positive sampling variances.
Is there any way around this?
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Sent: 27 August 2014 13:36
To: Owen, Branwen
Subject: Metafor -can't calculate heterogeneity with non-positive sampling variances
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