Margin of Error

by Jeff Sauro, PhD | August 6, 2009

Browse Content by Topic

UX ( 73 )
Methods ( 62 )
Usability Testing ( 53 )
Statistics ( 51 )
Survey ( 36 )
Benchmarking ( 32 )
Usability ( 32 )
NPS ( 31 )
Customer Experience ( 30 )
User Research ( 28 )
SUS ( 25 )
Rating Scale ( 21 )
Net Promoter Score ( 21 )
Sample Size ( 19 )
Usability Problems ( 17 )
Metrics ( 16 )
Measurement ( 15 )
Validity ( 14 )
User Experience ( 14 )
Satisfaction ( 13 )
Usability Metrics ( 13 )
Questionnaires ( 13 )
SUPRQ ( 12 )
Qualitative ( 11 )
Surveys ( 11 )
Navigation ( 10 )
Rating Scales ( 10 )
Market Research ( 9 )
Reliability ( 9 )
SUPR-Q ( 9 )
Task Time ( 8 )
Heuristic Evaluation ( 8 )
UX Metrics ( 8 )
Questionnaire ( 7 )
Task Completion ( 7 )
Mobile Usability Testing ( 6 )
UMUX-lite ( 6 )
Analytics ( 6 )
Mobile ( 6 )
Research ( 5 )
Six Sigma ( 5 )
Usability Problem ( 5 )
SEQ ( 5 )
Unmoderated Research ( 5 )
Visualizing Data ( 5 )
UX Methods ( 4 )
Quantitative ( 4 )
Moderation ( 4 )
Task Times ( 4 )
Loyalty ( 4 )
Confidence Intervals ( 4 )
UX Maturity ( 4 )
Credibility ( 4 )
Expert Review ( 4 )
Confidence ( 4 )
ROI ( 3 )
Task Metrics ( 3 )
Card Sorting ( 3 )
Customer Segmentation ( 3 )
Lean UX ( 3 )
PURE ( 3 )
Usability Lab ( 3 )
Desirability ( 3 )
Correlation ( 2 )
Marketing ( 2 )
Excel ( 2 )
Remote Usability Testing ( 2 )
PhD ( 2 )
Branding ( 2 )
Data ( 2 )
Prototype ( 2 )
Eye-Tracking ( 2 )
Salary Survey ( 2 )
Tasks ( 2 )
Key Driver ( 2 )
UX Salary Survey ( 2 )
Summative ( 2 )
Findability ( 2 )
A/B Testing ( 2 )
KLM ( 2 )
Cognitive Walkthrough ( 2 )
IA ( 2 )
Tree Testing ( 2 )
Focus Groups ( 2 )
Personas ( 2 )
SUM ( 2 )
Microsoft Desirability Toolkit ( 1 )
NSAT ( 1 )
Voice Interaction ( 1 )
User-Centred Design ( 1 )
LTR ( 1 )
PSSUQ ( 1 )
TAM ( 1 )
CSUQ ( 1 )
Delight ( 1 )
Customer effort ( 1 )
Desktop ( 1 )
Problem Severity ( 1 )
Information Architecture ( 1 )
RITE ( 1 )
Contextual Inquiry ( 1 )
MUSiC ( 1 )
ISO ( 1 )
Cumulative Graphs ( 1 )
History of usability ( 1 )
Meeting software ( 1 )
Formative testing ( 1 )
CUE ( 1 )
UEQ ( 1 )
Likert ( 1 )
Site Analytics ( 1 )
consumer software ( 1 )
b2b software ( 1 )
Mobile Usability ( 1 )
Hedonic usability ( 1 )
AttrakDiff2 ( 1 )
meCUE2.0 ( 1 )
Certification ( 1 )
Segmentation ( 1 )
Think Aloud ( 1 )
Persona ( 1 )
Random ( 1 )
Crowdsourcing ( 1 )
Five ( 1 )
Sample ( 1 )
Software ( 1 )
User Testing ( 1 )
Effect Size ( 1 )
True Intent ( 1 )
Visual Appeal ( 1 )
Trust ( 1 )
Top Task Analysis ( 1 )
Formative ( 1 )
Unmoderated ( 1 )
Design Thinking ( 1 )
Design ( 1 )
Ordinal ( 1 )
Perceptions ( 1 )
Quality ( 1 )
protoype ( 1 )
Facilitation ( 1 )
Test Metrics ( 1 )
Task Randomization ( 1 )
Moderating ( 1 )
Margin of Error ( 1 )
Metric ( 1 )
Errors ( 1 )
Competitive ( 1 )
Regression Analysis ( 1 )
Z-Score ( 1 )
Performance ( 1 )
Conjoint Analysis ( 1 )
Affinity ( 1 )
Task Completin ( 1 )
Expectations ( 1 )
moderated ( 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