By: Jeff Sauro • April 17, 2012
Compare two independent proportions for A/B testing or comparing completion rates or conversion rates for small and large sample sizes. Uses the N-1 Two proportion test and Fisher Exact test to generate p-values.[Read More]
By: Jeff Sauro • October 1, 2006
Use this calculator to determine the number of users you'd need to test given the probability of detecting a problem. If the probability of detecting the problem is unknown, this calculator also allows you to estimate the problem occurrence (p) from sample data.[Read More]
By: Jeff Sauro • February 6, 2006
Visualizing your task time data is an essential step in understanding its distribution and computing accurate confidence intervals. This calculator creates a dot-plot of your task times, transforms the raw data to adjust for non-normality and computes the intervals.[Read More]
By: Jeff Sauro • October 1, 2005
If you've wanted to provide a confidence interval around a small sample completion rate but just didn't have time to do the math, this calculator does the work for you.[Read More]
By: Jeff Sauro • January 4, 2008
Use this interactive calculator to understand how the sample size changes will affect the confidence interval around a completion rate.[Read More]
By: Jeff Sauro • December 3, 2007
Look up the area under the normal curve (1 or two-sided areas) from a standard score (Z-score).[Read More]
By: Jeff Sauro • December 4, 2007
Enter the area under the normal curve (a proportion between 0 & 1) and get the Z-critical value.[Read More]
By: Jeff Sauro • December 14, 2007
Use this interactive normal curve to understand how the z-score and the area of the curve are related. Offers both one and two-sided options.[Read More]
By: Jeff Sauro • June 5, 2009
Used for comparing 2 small sample binary completion rates (it uses a statistical test called the Fisher Exact Test)[Read More]
By: Jeff Sauro • March 21, 2012
Compute confidence intervals around continuous data using either raw or summary data.[Read More]
Jeff Sauro is the founding principal of Measuring Usability LLC, a company providing statistics and usability consulting to
Fortune 1000 companies.
He is the author of over
15 journal articles and 4 books on statistics and the user-experience.
More about Jeff...
10 Metrics for Testing Website Navigation
Five Techniques for Moderating Usability Tests
5 Examples of Quantifying Qualitative Data
What five users can tell you that 5000 cannot
8 Ways to Show Design Changes Improved the User Experience
10 Things to Know about Usability Problems
The Five Most Influential Papers in Usability
Confidence Interval Calculator for a Completion Rate
Should you use 5 or 7 point scales?
Does better usability increase customer loyalty?
How to Conduct a Usability test on a Mobile Device
97 Things to Know about Usability
Nine misconceptions about statistics and usability
A Brief History of the Magic Number 5 in Usability Testing
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 | Excel & R Companion to Quantifying the User Experience Detailed Steps to Solve over 100 Examples and Exercises in the Excel Calculator and R Buy on Amazon | Download |
 | A Practical Guide to the System Usability Scale Background, Benchmarks & Best Practices for the most popular usability questionnaire Buy on Amazon | Download |
 | A Practical Guide to Measuring Usability 72 Answers to the Most Common Questions about Quantifying the Usability of Websites and Software Buy on Amazon | Download |