Value Metric
Usability Quality Index (UQI)
The Usability Quality Index (UQI) combines usability signals into a single composite score for tracking experience quality.
What is Usability Quality Index (UQI)?
The Usability Quality Index is a composite measure that blends multiple usability signals — such as task success, time on task, error rate, and perceived ease — into one index. Rather than watching several metrics separately, teams roll them into a single number that summarizes the overall quality of a usability experience and is easy to track over time.
As a composite, its value depends on choosing the right component metrics and weighting them to reflect what quality means for your product.
How to calculate it
UQI = Weighted combination of standardized usability component scores
- Component scores
- Standardized inputs (e.g. task success, time, errors, ease)
- Weights
- Relative importance assigned to each component
Worked example
Standardize each component to a common scale, apply your chosen weights, and average them into a single 0–100 index.
What good looks like
- Composite, track internallyTrend over absolute
Because the exact composition varies by team, cross-company benchmarks are not meaningful. Define components once and track the index over releases.
Why it matters
A single composite index is easier to communicate and rally around than a scatter of separate usability metrics, and it prevents cherry-picking whichever number looks best. The trade-off is transparency: a composite can hide which underlying signal moved, so keep the components visible alongside the index.
How to improve Usability Quality Index (UQI)
Improve the weakest component
Decompose the index and target the component metric — success, time, errors, or ease — that is dragging it down.
Validate the weighting
Check that your component weights reflect what actually matters to users, adjusting as you learn.
Frequently asked questions
What goes into a Usability Quality Index?
Typically a mix of behavioral and attitudinal usability signals — task success rate, time on task, error rate, and a perceived-ease measure — standardized and combined. The exact components and weights are chosen to reflect what quality means for your product.
Should you use a composite index or individual metrics?
Both. A composite is useful for communicating overall trend and preventing cherry-picking, but you should keep the underlying metrics visible so you can see which signal changed and act on it. The index summarizes; the components diagnose.