This page has a large assortment of web-based calculators and tools for statistical and evaluation purposes including percent change, required sample size, margin of error, effect size, statistical power, and others.
Comprehensive Set of Calculators
This site offers a lengthy list of calculators covering a wide array of statistical purposes. Includes over 600 links and almost 400 calculating pages!
- Chart Builder for Excel and PowerPoint
Difference of Proportions (Z-test)
Sample Size / Margin of Error
- EZ-SRS-SS for Random Samples developed by Organizational Development
Sample size for proportions, means, and totals.
- EZ-SRS-ME for Random Samples developed by Organizational Development
Margin of error for proportions, means, and totals. Reports both question-level and response category-level margin of errors for up to 8 response categories in a single survey question.
- Calculator for Random Samples #1
Sample size and margin of error for proportions (assumes proportion of 0.5 for most conservative estimate).
- Calculator for Random Samples #2
Sample size and margin of error for proportions (enter proportion for greater precision).