Margin of Error

by Jeff Sauro, PhD | August 6, 2009

Browse Content by Topic

UX ( 62 )
Methods ( 52 )
Usability Testing ( 52 )
Statistics ( 51 )
Usability ( 32 )
Survey ( 32 )
User Research ( 27 )
Benchmarking ( 27 )
Customer Experience ( 26 )
SUS ( 21 )
NPS ( 21 )
Sample Size ( 18 )
Usability Problems ( 17 )
Net Promoter Score ( 15 )
Rating Scale ( 14 )
Usability Metrics ( 13 )
Metrics ( 13 )
SUPRQ ( 12 )
Measurement ( 12 )
User Experience ( 11 )
Qualitative ( 11 )
Navigation ( 10 )
Task Time ( 8 )
Surveys ( 8 )
Market Research ( 8 )
UX Metrics ( 7 )
Questionnaires ( 7 )
Task Completion ( 7 )
Heuristic Evaluation ( 7 )
Questionnaire ( 6 )
Reliability ( 6 )
Mobile ( 6 )
Mobile Usability Testing ( 6 )
Analytics ( 5 )
Usability Problem ( 5 )
Validity ( 5 )
Rating Scales ( 5 )
Visualizing Data ( 5 )
Six Sigma ( 5 )
Satisfaction ( 5 )
Research ( 4 )
Confidence ( 4 )
UX Maturity ( 4 )
Confidence Intervals ( 4 )
Task Times ( 4 )
Quantitative ( 4 )
Credibility ( 4 )
Loyalty ( 4 )
Moderation ( 4 )
Customer Segmentation ( 3 )
Expert Review ( 3 )
Card Sorting ( 3 )
SUPR-Q ( 3 )
SEQ ( 3 )
Task Metrics ( 3 )
Unmoderated Research ( 3 )
Lean UX ( 3 )
Usability Lab ( 3 )
ROI ( 3 )
Eye-Tracking ( 2 )
Excel ( 2 )
Summative ( 2 )
PhD ( 2 )
Salary Survey ( 2 )
IA ( 2 )
Key Driver ( 2 )
Marketing ( 2 )
Tree Testing ( 2 )
Data ( 2 )
UX Methods ( 2 )
Remote Usability Testing ( 2 )
SUM ( 2 )
Personas ( 2 )
A/B Testing ( 2 )
UX Salary Survey ( 2 )
Findability ( 2 )
KLM ( 2 )
Certification ( 2 )
Tasks ( 2 )
UMUX-lite ( 2 )
Correlation ( 2 )
PURE ( 2 )
Branding ( 2 )
Focus Groups ( 2 )
Cognitive Walkthrough ( 2 )
protoype ( 1 )
Z-Score ( 1 )
Facilitation ( 1 )
Perceptions ( 1 )
Site Analytics ( 1 )
Metric ( 1 )
Contextual Inquiry ( 1 )
Prototype ( 1 )
Mobile Usability ( 1 )
Performance ( 1 )
moderated ( 1 )
Affinity ( 1 )
Task Completin ( 1 )
Moderating ( 1 )
Information Architecture ( 1 )
Problem Severity ( 1 )
Test Metrics ( 1 )
Trust ( 1 )
Persona ( 1 )
Segmentation ( 1 )
Software ( 1 )
Ordinal ( 1 )
User Testing ( 1 )
Effect Size ( 1 )
True Intent ( 1 )
Visual Appeal ( 1 )
Top Task Analysis ( 1 )
Design ( 1 )
Unmoderated ( 1 )
Regression Analysis ( 1 )
Conjoint Analysis ( 1 )
Random ( 1 )
Margin of Error ( 1 )
Crowdsourcing ( 1 )
Sample ( 1 )
Five ( 1 )
Task Randomization ( 1 )
Quality ( 1 )
Competitive ( 1 )
Expectations ( 1 )
Formative ( 1 )
Errors ( 1 )
Think Aloud ( 1 )
Desktop ( 1 )

Margins of Error in Usability Tests

By Jeff Sauro, PhD . August 6, 2009 . Tags: Margin of Error, Task Metrics, Statistics

How many users will complete the task and how long will it take them? If you need to benchmark an interface, then a summative usability test is one way to answer these questions. Summative tests are the gold-standard for usability measurement. But just how precise are the metrics? Just as a presidential poll uses a sample to estimate outcomes for the entire population, usability tests