Information about effect size (standardized mean difference):


Wikipedia’s overview of effect size is readable and informative:


Overview and calculator by Lee Becker of the University of Colorado at Colorado Springs (UCCS)


Thalheimer, W., & Cook, S. (2002, August). How to calculate effect sizes from published research articles: A simplified methodology.


Other effect size calculators and graphing software:


Effect Size Calculator


Centre for Evaluation & Monitoring Effect Size Calculator and Graphing tool


Bolder Stats Cohen’s d and Distribution Overlap applet


Claremount Graduate University Web Interface for Statistical Education Statistical Power Applet:


Calculators and illustrators for dichotomous measures:


Understanding Uncertainty: Spinning the Risk (University of Cambridge)


Visual Rx - Online NNT Calculator


Confidence interval calculator for NNTs and much more (by Robert Herbert, University of Sydney)


Centre for Evidence Based Medicine, University Health Network (Toronto)