Effective use of Pearson's product-moment correlation coefficient Comment

The calculation of correlation coefficients is widespread in biological research. Often, the null hypothesis of zero correlation is tested and/or confidence intervals for the correlation are computed. There are several different methods for this purpose; we compare the performance of different methods. According to our results the standard t test approach does offer generally reasonable performance even when the underlying distribution departs from bivariate normality. However, for non-normal data alternative techniques, especially the permutation test and using the RIN (rank-based inverse normal) transformation, offer better control of type I error and good power. With regard to confidence intervals, all investigated methods perform similarly; and there is no consistent pattern with which to strongly recommend one method over another. However, we show that two easy-to-calculate methods based on asymptotic results often perform tolerably well even for small sample sizes. (C) 2014 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.