Jeff Sauro • January 4, 2008

Use this calculator to understand how sample size changes will affect the confidence interval around a completion rate. For more context, see the Sample Size article.Known Users: Most Likely Completion Rates

Known Minimum Completion Rate: Unknown Users

The calculations are derived from the Adjusted-Wald binomial confidence interval.

10 Golden Rules of Facilitation

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A Brief History of the Magic Number 5 in Usability Testing

What five users can tell you that 5000 cannot

How to Conduct a Usability test on a Mobile Device

97 Things to Know about Usability

Nine misconceptions about statistics and usability

The Five Most Influential Papers in Usability

Should you use 5 or 7 point scales?

Does better usability increase customer loyalty?

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

8 Ways to Show Design Changes Improved the User Experience

10 Things to Know about Usability Problems

How common are usability problems?

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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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