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

The New Face of Usability Testing

7 Techniques for Prioritizing Customer Requirements

How to Compute a Confidence Interval in 5 Easy Steps

The Experiment Requires That You Continue: On The Ethical Treatment of Users

How common are usability problems?

Should you use 5 or 7 point scales?

5 Examples of Quantifying Qualitative Data

Confidence Interval Calculator for a Completion Rate

Nine misconceptions about statistics and usability

The Five Most Influential Papers in Usability

10 Things to Know about Usability Problems

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

Does better usability increase customer loyalty?

97 Things to Know about Usability

8 Ways to Show Design Changes Improved the User Experience

A Brief History of the Magic Number 5 in Usability Testing

How to Conduct a Usability test on a Mobile Device

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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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