## 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 … Read more

## Solved – How to convert \$eta^2\$ to Pearson’s r

I am doing a meta-analysis of associations between sets of variables that are essentially all continuous. However, many studies operationalised them at 'lower' levels, and I have (converted to) most effect sizes you can think of (Cohen's \$d\$, Pearson's \$r\$, Cramer's \$V\$, \$eta^2\$, \$omega^2\$, and \$OR\$'s). Converting between most of these is no problem (that … Read more

## Solved – Orwin’s fail safe N test

In Orwin's fail safe N test how to decide the values of criterion for a trivial log odd's ratio and mean log odds ratio in missing studies. I am a medical doctor. Please tell me in simple english. The data are 1. Classic fail-safe N Z-value for observed studies 27.97543 P-value for observed studies 0.00000 … Read more

## Solved – How to combine data from 2 separate experiments

I am a scientist and by no means a statistician. I have, I think, a very basic question for you all. I have performed the same experiment twice (analyzing levels of a certain protein) and am comparing levels in untreated vs treated animals. I performed a t-test with welch correction (because there was significant variance). … Read more

## Solved – Can a meta-analysis of studies which are all “not statistically signficant” lead to a “significant” conclusion

A meta-analysis includes a bunch of studies, all of which reported a P value greater than 0.05. Is it possible for the overall meta-analysis to report a P value less than 0.05? Under what circumstances? (I am pretty sure the answer is yes, but I'd like a reference or explanation.) Best Answer In theory, yes… … Read more

## Solved – Deriving effect sizes form pre-post treatment design in R

This question is related to my previous post. In case of a meta-analysis of a pre-post treatment design I have data given from 5 studies that tested subjects pre- and post-treatment on a continuous scale (means and standard deviation are available pre- and post-treatment). Moreover every study has tested 4 subgroups. Here is some dummy … Read more

## Solved – Deriving effect sizes form pre-post treatment design in R

This question is related to my previous post. In case of a meta-analysis of a pre-post treatment design I have data given from 5 studies that tested subjects pre- and post-treatment on a continuous scale (means and standard deviation are available pre- and post-treatment). Moreover every study has tested 4 subgroups. Here is some dummy … Read more

## Solved – Why do we log transform response ratios

In meta-analysis, it seems a standard practice to take the natural log of the response ratio before evaluating it. My question is why? That is, if I have a treatment mean (Xe) and a control mean of (Xc), and the response ratio (RR) is defined as Xe/Xc, why would I take the natural logarithm of … Read more

## Solved – Why do we log transform response ratios

In meta-analysis, it seems a standard practice to take the natural log of the response ratio before evaluating it. My question is why? That is, if I have a treatment mean (Xe) and a control mean of (Xc), and the response ratio (RR) is defined as Xe/Xc, why would I take the natural logarithm of … Read more

## Solved – How to carry out adjusted indirect comparison or ‘Bucher method’ meta-analysis

I have carried out a pairwise meta-analysis of Drug 1 vs. placebo and a pairwise meta-analysis of Drug 2 vs. placebo (I have used RevMan software to do this). From each meta-analyses I have an overall estimate of the log of the risk ratio, accompanied by a standard error. I want to use the 'Bucher … Read more