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.

Getting Started Finding the Right Sample Size

The Essentials of a Contextual Inquiry

Should you use 5 or 7 point scales?

8 Ways to Show Design Changes Improved the User Experience

The Five Most Influential Papers in Usability

Confidence Interval Calculator for a Completion Rate

What five users can tell you that 5000 cannot

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

How common are usability problems?

97 Things to Know about Usability

How to Conduct a Usability test on a Mobile Device

A Brief History of the Magic Number 5 in Usability Testing

5 Examples of Quantifying Qualitative Data

Nine misconceptions about statistics and 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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