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

6 Ways to Visualize Statistical Significance

Reflecting on the One-Way Mirror

What five users can tell you that 5000 cannot

10 Things to Know about Usability Problems

Does better usability increase customer loyalty?

8 Ways to Show Design Changes Improved the User Experience

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

Nine misconceptions about statistics and usability

5 Examples of Quantifying Qualitative Data

How common are usability problems?

How to Conduct a Usability test on a Mobile Device

Confidence Interval Calculator for a Completion Rate

97 Things to Know about Usability

Should you use 5 or 7 point scales?

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

Quantifying the User Experience 2nd Ed.: Practical Statistics for User ResearchThe most comprehensive statistical resource for UX Professionals Buy on Amazon | |

Excel & R Companion to the 2nd Ed. of 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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