Jeff Sauro • December 4, 2007
Enter the area under the normal curve (a proportion between 0 & 1) and get the Z-critical value, one-sided or two-sided. To convert a Z-Score into a percentage use the Z-Score to Percentile Calculator. See also the interactive Graph of the Standard Normal Curve.
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...
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Five Techniques for Moderating Usability Tests
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Why you only need to test with five users (explained)
Should you use 5 or 7 point scales?
How to Conduct a Usability test on a Mobile Device
Nine misconceptions about statistics and usability
Confidence Interval Calculator for a Completion Rate
How common are usability problems?
What five users can tell you that 5000 cannot
97 Things to Know about Usability
A Brief History of the Magic Number 5 in Usability Testing
5 Examples of Quantifying Qualitative Data
8 Ways to Show Design Changes Improved the User Experience
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