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. 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 for scientists themselves effect sizes are most useful because they facilitate cumulative science effect sizes can be used to determine the sample size . 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 for scientists themselves effect sizes are most useful because they facilitate . Instead of a complete overview of effect sizes in exper the aim of this article was to provide a practical primer on imental research eg grissom and kim 2005 i have tried to how to calculate and report effect sizes to facilitate cumulative provide a practical primer that aims to be an time efficient but science with a focus on t tests and anovas current prac complete overview of . For scientists themselves effect sizes are most useful because they facilitate cumulative science effect sizes can be used to determine the sample size for follow up studies or examining effects across studies this article aims to provide a practical primer on how to calculate and report effect sizes for t tests and anovas such that effect sizes can be used in a priori power analyses