[2022] On generalized eta squared tab, corrected cell BB15 to =BB5/(BB5+AX7+AY7+BA7+BC7) (thanks to Samsoon Inayat) and cells BP and BQ now have correct labels MS_B and MS_AB (thanks to Amanda Kay Montoya) [2019] Corrected formula for 95% CI around mean difference in independent t-test to prevent error with unequal n (thanks to Michael Cantinotti). I've updated the unbiased effect size calculation for within designs to match recommendations by Cumming (2012) I've added an effect size conversion spreadsheet (From_R2D2) to the files section. See [this blog post][1] for more information. This article is published at Frontiers in Cognition. It's Open Access, and you can download it here: http://www.frontiersin.org/Journal/Abstract.aspx?s=194&name=cognition&ART_DOI=10.3389/fpsyg.2013.00863 If you found it useful and want to cite it, you can do so as: Lakens, D. (2013) Calculating and reporting effect sizes to facilitate cumulative science: A practical primer for t-tests and ANOVAs. Frontiers in Psychology, 4:863. doi:10.3389/fpsyg.2013.00863 [1]: https://sites.google.com/site/lakens2/blog/fromr2d2