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.Download this calculator in an excel file or take a Crash course in Z-scores

3 Days of Hands-On Training on User Experience Methods, Metrics and Analysis.Learn More

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The Five Most Influential Papers in Usability

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97 Things to Know about Usability

How common are usability problems?

Why you only need to test with five users (explained)

Nine misconceptions about statistics and usability

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Quantifying the User Experience: Practical Statistics for User ResearchThe most comprehensive statistical resource for UX Professionals Buy on Amazon | |

Excel & R Companion to Quantifying the User ExperienceDetailed 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 ScaleBackground, Benchmarks & Best Practices for the most popular usability questionnaire Buy on Amazon | Download | |

A Practical Guide to Measuring Usability72 Answers to the Most Common Questions about Quantifying the Usability of Websites and Software Buy on Amazon | Download |

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