ranktest.rma {metafor}R Documentation

Rank Correlation Test for Funnel Plot Asymmetry for rma Objects

Description

Rank correlation test for funnel plot asymmetry for objects of class "rma".

Usage

## S3 method for class 'rma':
ranktest(x, ...)

Arguments

x an object of class "rma".
... other arguments.

Details

The function carries out the rank correlation test as described by Begg and Mazumdar (1994). The test can be used to examine whether the observed outcomes and the corresponding sampling variances are correlated. A high correlation would indicate that the funnel plot is asymmetric, which may be a result of publication bias.

Value

An object of class "ranktest.rma". The object is a list containing the following components:

tau the estimated value of Kendall's tau rank correlation coefficient
pval the corresponding p-value for the test that the true tau is equal to zero


The results are formated and printed with the print.ranktest.rma function.

Note

The method does not depend on the model fitted. Therefore, regardless of the model, the results of the rank test will always be the same. See regtest for tests of funnel plot asymmetry that are based on regression models and model dependent.

The function makes use of the cor.test function with method="kendall". If possible, an exact p-value is provided; otherwise, a large-sample approximation is used.

Author(s)

Wolfgang Viechtbauer; wvb@www.wvbauer.com; http://www.wvbauer.com/

References

Begg, C. B. & Mazumdar, M. (1994) Operating characteristics of a rank correlation test for publication bias. Biometrics, 50, 1088–1101.

See Also

ranktest, regtest

Examples

### load BCG vaccine data
data(dat.bcg)

### calculate log risk ratios and corresponding sampling variances
dat <- escalc(measure="RR", ai=tpos, bi=tneg, ci=cpos, di=cneg, data=dat.bcg)
dat <- cbind(dat.bcg, dat)

### random-effects model
res <- rma(yi, vi, data=dat, method="REML")

ranktest(res)

[Package metafor version 0.5-5 Index]