- Calculation of sample size: Sample size, to specify the number of participants necessary to demonstrate the training effect, will be calculated from the training effect size between the Start index and the Max index provided by CogMed training. Based on a previous pilot study in our institute (effect size =.54) and on findings by Lundqvist and collaborators (2010) (effect size=.95), the effect size estimates for this study will be .60 and the sample size 20 children.