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

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

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

Should you use 5 or 7 point scales?

8 Ways to Show Design Changes Improved the User Experience

5 Examples of Quantifying Qualitative Data

How to Conduct a Usability test on a Mobile Device

10 Things to Know about Usability Problems

97 Things to Know about Usability

Nine misconceptions about statistics and usability

What five users can tell you that 5000 cannot

How common are usability problems?

A Brief History of the Magic Number 5 in Usability Testing

Does better usability increase customer loyalty?

.

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 |

.

.

.