Jeff Sauro • December 3, 2007

Enter a z-critical value and get the area under the normal curve (a percentage). Selecting two-sided provides the area above Z and below -Z. Selecting one side provides the area only above or below the Z-value. See also the interactive Graph of the Standard Normal Curve. To convert a percentage into a Z-Score use the Percentile to Z-Score Calculator.Download this calculator in an excel file or take a Crash course in Z-scores

Getting Started Finding the Right Sample Size

The Essentials of a Contextual Inquiry

Confidence Interval Calculator for a Completion Rate

The Five Most Influential Papers in Usability

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

Nine misconceptions about statistics and usability

Does better usability increase customer loyalty?

10 Things to Know about Usability Problems

A Brief History of the Magic Number 5 in Usability Testing

What five users can tell you that 5000 cannot

How common are usability problems?

8 Ways to Show Design Changes Improved the User Experience

How to Conduct a Usability test on a Mobile Device

97 Things to Know about Usability

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Customer Analytics for DummiesA guidebook for measuring the customer experience Buy on Amazon | |

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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