Glossary
Searchable terminology from accessibility, web standards, and related fields.
15 results found in metrics.
- Accessibility Metric (Web Accessibility Metric, Accessibility Score)
- A quantitative measure used to assess and compare the accessibility quality of web pages or websites. Accessibility metrics typically calculate a score (often 0-100%) based on the number and severity …
- Barrier Impact Factor (BIF, Accessibility Barrier Impact)
- A metric for measuring the severity of web accessibility barriers by weighting detected errors according to which assistive technologies and disability groups they affect. The BIF is calculated by sum…
- Character Error Rate (CER)
- A metric for evaluating automatic speech recognition (ASR) and optical character recognition (OCR) accuracy, measuring the minimum number of character-level edits (insertions, deletions, substitutions…
- Communication Rate (Communication Speed)
- The speed at which a person can convey messages, typically measured in words per minute (WPM). For AAC users, communication rate is often significantly slower than natural speech (100-200 WPM)—unaided…
- Input Rate (Keystroke Rate)
- The speed at which a user can produce individual keystrokes or character inputs, typically measured in seconds per keystroke. Input rate varies dramatically across access methods: touch typists may ac…
- Keystroke Saving Rate (KSR, Keystroke Savings)
- A metric measuring the efficiency of text prediction systems by calculating the percentage of keystrokes saved compared to typing the same text on a standard keyboard without prediction. A KSR of 50% …
- Keystroke Savings (KS, Key Savings)
- A metric used to evaluate word prediction systems, measuring the percentage of keystrokes eliminated by accepting predictions compared to typing the full text character by character. While keystroke s…
- Prediction Utilization (PU)
- The percentage of opportunities where a user accepts a word prediction rather than continuing to type the word manually. Prediction utilization reflects user trust in a prediction system—higher qualit…
- Reaching Time (Navigation Time, Time to Target)
- A usability metric measuring the time required for a user to navigate to a specific element on a web page. For blind users employing screen readers, reaching time is a key indicator of page navigabili…
- Response Time (Reaction Time, Tact)
- The time elapsed between the presentation of a stimulus and the user's physical response, typically measured in milliseconds. In scanning-based AAC, response time (often called Tact) is the interval b…
- Throughput (Throughput (Fitts), Pointing Throughput)
- In human-computer interaction, throughput is a combined speed-accuracy metric derived from Fitts's law that measures the efficiency of aimed pointing movements, expressed in bits per second (bps). It …
- Unified Web Evaluation Methodology (UWEM)
- A standardized methodology developed by the European Web Accessibility Benchmarking Cluster (WAB Cluster) for evaluating the accessibility of websites in a consistent, comparable way. UWEM provides fo…
- Violation Score (Accessibility Score, A11y Score)
- A numerical metric used to quantify the severity and prevalence of accessibility violations on a web page or within a dataset. Violation scores typically map qualitative impact levels (cosmetic, minor…
- Visual acuity (VA, LogMAR acuity, Snellen acuity)
- A measure of the sharpness or clarity of vision, typically expressed as a Snellen fraction (e.g., 20/20, 20/200) or LogMAR value. A person with 20/200 vision must be 20 feet away to see what someone w…
- Word error rate (WER)
- The standard metric for evaluating automatic speech recognition accuracy, calculated as the number of substitutions, deletions, and insertions divided by the total number of words in the reference tra…