The aim of this article was to provide a practical primer on how to calculate and report effect sizes to facilitate cumulative science with a focus on t tests and anovas current practices in the way researchers report effect sizes can be improved first researchers should always report effect sizes. Calculating and reporting effect sizes to facilitate cumulative science a practical primer for t tests and anovas daniel lakens human technology interaction group eindhoven university of technology eindhoven netherlands edited by bernhard hommel leiden university netherlands reviewed by marjan bakker university of amsterdam netherlands. General discussionthe aim of this article was to provide a practical primer on how to calculate and report effect sizes to facilitate cumulative science with a focus on t tests and anovas current practices in the way researchers report effect sizes can be improved first researchers should always report effect sizes. T1 calculating and reporting effect sizes to facilitate cumulative science a practical primer for t tests and anovas au lakens d py 2013 y1 2013 n2 effect sizes are the most important outcome of empirical studies most articles on effect sizes highlight their importance to communicate the practical significance of results. The aim of this article was to provide a practical primer on how to calculate and report effect sizes to facilitate cumulative science with a focus on t tests and anovas current practices in the way researchers report effect sizes can be improved first researchers should always report effect sizes