Statistical Calculators

• Free Power and Sample Size Estimation Software
• SOCR:Statistics Online Computational Resource
• Free Software for Converting Relative Risks to Absolute Risks
• P and Critical Value Calculator
• MGH Clincial Trial Sample Size Calculator
• Software from Basagaña and Spiegelman for sample size and power for longitudinal studies
• More R functions for sample size estimation for longitudinal studies
• statpages.org

Prognostic and Diagnostic Calculators

• http://www.marionsmits.net/chip-prediction-rule
• Center for Evidence Based Medicine Calculator, including calculations for diagnostic accuracy measures