152017-03-13 16:19:06PeterWatson142013-03-08 10:17:09localhostconverted to 1.6 markup132011-06-21 12:48:09PeterWatson122011-06-01 09:32:25PeterWatson112009-04-01 13:54:08PeterWatson102009-03-20 11:16:43PeterWatson92009-03-20 11:16:25PeterWatson82009-03-20 11:07:30PeterWatson72009-03-20 11:07:10PeterWatson62009-03-19 15:11:51PeterWatson52009-03-19 15:11:11PeterWatson42009-03-19 15:06:29PeterWatson32007-01-25 15:55:49PeterWatson22007-01-24 16:36:53PeterWatson12007-01-24 16:34:10PeterWatson

This spreadsheet evaluates the average correlation for a set of upto 100 inputted correlations. The program Fisher z-transforms the raw correlations, works out the average of the transformed correlation and then backtransforms it. Fisher z transformed correlations are used in areas such as meta-analysis for computing overall estimates of correlations such as those obtained by pooling over studies (Field AP and Gillett R, 2010). Fisher z-transformed correlations are also usually used when comparing average correlations between groups. Bonett DG (2008) further recommends and illustrates a simple way of computing a variance for the average of correlations obtained from different studies which he then uses to obtain a 95% confidence interval for the average correlation. This method uses the mean of the raw correlations as a point estimate. Bonett performs a series of simulation studies which show his derived 95% confidence intervals have better coverage than the more traditional approaches such as Hedges-Olkin (1985). In one example (which is the one in the spreadsheet mentioned below), he finds the supposed 95% confidence interval using Hedges-Olkin is only a 57% one! This spreadsheet evaluates Bonett's (2008) recommended confidence interval for the average correlation and one of the older methods which uses the mean of the Fisher z-transformed correlations, the Hedges-Olkin (1985). If one is using time series data it may be worth considering removing autocorrelations by differencing successive observations prior to computing a correlation in order to remove this. Reference Bonett, DG (2008) Meta-analytic interval estimation for bivariate correlations. Psychological Methods 13(3) 173-181. (This paper is downloadable by CBSU users for free using ScienceDirect). Field, AP and Gillett, R (2010) How to do a meta-analysis. British Journal of Mathematical and Statistical Psychology 63 665-694. Hedges, LV, & Olkin, I (1985) Statistical methods in metaanalysis. Orlando, FL: Academic Press.