Confidence Intervals and Correlations

In a previous post, I discussed the various scenarios for running significance tests on correlations.

A researcher recently asked me how to calculate confidence intervals for two correlations that share a common variable (i.e., dependent correlations).

Normality and Transformations: A few thoughts

A lot of researchers ask me about normality and transformations. This post sets out some my advice on assessing normality and dealing with violations of the assumption.

Bootstrapping and the boot package in R

I was recently asked about options for bootstrapping. The following post sets out some applications of bootstrapping and strategies for implementing it in R. I've found bootstrapping useful in several settings:

• where the statistic I'm interested in is a little unusual: the average R-square across five separate regressions; the difference in the average correlation of a set of variables between two groups
• non parametric statistics, such as the median
• when assumptions such as normality of homoscedasticity are not satisfied