WebPower is a collection of tools for conducting statistical power analysis online. WebPower can be used by anyone for free. To use the software now, click here. For a short tutorial on how to use WebPower, click here. For the free online manual book (more than 30MB), please click here. To order a hard copy of the book, click the book cover below:

To cite WebPower, please use:

Zhang, Z., & Yuan, K.-H. (2018). Practical Statistical Power Analysis Using Webpower and R (Eds). Granger, IN: ISDSA Press.

• Diagram based power analysis

• Correlation based on Z-test

• One sample proportion
• Two sample proportion, equal sample size
• Two sample proportion, unequal sample size

• Power of t-test
• Power of t test (Unbalanced sample sizes)
• Balanced one-way ANOVA
• Two-way and three-way ANOVA with interaction
• Repeated-measures ANOVA

• Linear regression
• Logistic regression
• Poisson regression

• Sample size calculation for a mixed model of repeated measures with general correlation structure
• Statistical power for a mixed model of repeated measures with AR(1) correlation structure

• Power analysis based on RMSEA (MacCallum et al., 1996)
• Power analysis using Satorra & Saris (1985)

• ANOVA example data set 1