Solved – Tau, Tau squared and I squared =0

I've used the confint() function of R package metafor to calculate heterogeneity in random effects models in a meta-analysis.

I get sensible values for the various parameters (tau, tau^2, I^2) for most of the calculations I have run, however am getting back 0 values for all three parameters for one particular analysis. I have checked the raw data and nothing looks suspiciously different to that used for other calculations.

The confint() output I get is as follows.

       estimate   ci.ub tau^2    0.0000 0.0000  0.1061 tau      0.0000 0.0000  0.3257 I^2(%)   0.0000 0.0000 60.4187 H^2      1.0000 1.0000  2.5264 

Does anyone have any idea about why I might be getting a 0 estimate with 0 as the lower end of the confidence interval?

Any thoughts would be much appreciated.

This is telling you that the data is homogenous but the degree of precision is not reported because it's less than 0.0001. For example your uncertainty intervals around the I-squared are 0% to 60%. For I-squared, it's a percentage and you can't get a negative number (only 0 – 100%) even if it makes it look skewed (as in this case).

Hope this helps.


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