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]
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 3 books on statistics and the user-experience.
More about Jeff...
Distrust in Social Networks: Google+, Twitter, Facebook
5 Examples of Quantifying Qualitative Data
Why you only need to test with five users (explained)
25 Resources for Measuring Usability
97 Things to Know about Usability
Does better usability increase customer loyalty?
Top 10 Research-Based Usability Findings of 2010
A Brief History of the Magic Number 5 in Usability Testing
10 Things to Know about Usability Problems
The Five Most Influential Papers in Usability
Confidence Interval Calculator for a Completion Rate
What five users can tell you that 5000 cannot
Should you use 5 or 7 point scales?
