Qualitative usability studies have few users and variable protocol; numbers obtained from such studies are likely to poorly reflect the true behavior of your population due to large measurement errors.| Nielsen Norman Group
Qualitative research informs the design process; quantitative research provides a basis for benchmarking programs and ROI calculations.| Nielsen Norman Group
Don’t report descriptive statistics like success rates and averages unless you ran a quantitative study. Reported numbers must be qualified with statistical information such as confidence intervals or statistical significance.| Nielsen Norman Group
A confidence-interval calculation gives a probabilistic estimate of how well a metric obtained from a study explains the behavior of your whole user population.| Nielsen Norman Group
Quantitatively evaluate a product or service’s user experience by using metrics to gauge its relative performance against a meaningful standard.| Nielsen Norman Group
Simple usability tests where users think out loud are cheap, robust, flexible, and easy to learn. Thinking aloud should be the first tool in your UX toolbox, even though it entails some risks and doesn't solve all problems.| Nielsen Norman Group
Elaborate usability tests are a waste of resources. The best results come from testing no more than 5 users and running as many small tests as you can afford.| Nielsen Norman Group
Prove the value of your design efforts by estimating return on investment.| Nielsen Norman Group
