Glossary
Searchable terminology from accessibility, web standards, and related fields.
25 results found in Metrics.
- Accessibility Metric (Web Accessibility Metric, Accessibility Quality Metric)
- An accessibility metric is a quantitative measure used to assess the level of accessibility compliance of a web page or website. Metrics typically derive from the results of automated or manual evalua…
- Accessibility Progress Formula (APPF, Accessibility Progress Percentage)
- A formula for quantitatively tracking progress in addressing accessibility issues on a website, expressed as APPF = A / ((A + B) + (T - C)), where A is the number of applicable checklist items that ha…
- Correctness (Precision, Validity)
- In the context of accessibility evaluation, correctness (also called precision) is the proportion of reported accessibility problems that are true problems — that is, issues that genuinely affect user…
- Dale-Chall Readability Formula (Dale-Chall, New Dale-Chall)
- A readability formula first published by Edgar Dale and Jeanne Chall in 1948 and revised in 1995. Unlike formulas that rely only on surface counts, Dale-Chall compares every word in a text against a m…
- Equal Error Rate (EER, Crossover Error Rate)
- A metric used to evaluate biometric system performance, representing the point at which the false acceptance rate (wrongly accepting unauthorized users) equals the false rejection rate (wrongly reject…
- Evaluation Reliability (Inter-rater Reliability, Evaluator Agreement)
- The extent to which independent accessibility evaluations of the same content produce consistent results. High reliability means that different evaluators using the same method will identify similar s…
- F-measure (F-score, F1 Score)
- A metric that combines correctness (precision) and sensitivity (recall) into a single balanced score, calculated as the harmonic mean of the two values. In accessibility evaluation research, the F-mea…
- Gunning Fog Index (Gunning FOG, FOG Index)
- A traditional readability formula developed by Robert Gunning in 1952 that estimates the years of formal education a reader needs to understand a text on first reading. It is calculated from average s…
- Keystroke Saving (KS, Keystroke Reduction)
- A metric used to evaluate word prediction and word completion systems, measuring the percentage of keystrokes that a user can avoid by accepting system predictions instead of typing each character ind…
- Keystrokes Per Character (KSPC)
- A metric used to evaluate the efficiency of text-entry methods by measuring the average number of keystrokes required to produce each character of text. A lower KSPC indicates a more efficient input m…
- Lexile Framework (Lexile, Lexile Measure)
- A commercial readability framework developed by MetaMetrics that places both texts and readers on a common scale — the Lexile measure — to support matching readers with materials at an appropriate lev…
- LogMAR (Logarithm of the Minimum Angle of Resolution)
- A standardised scale for measuring visual acuity based on the logarithm (base 10) of the minimum angle of resolution, used in the Bailey-Lovie eye chart and widely adopted in clinical vision research.…
- Minimum String Distance (MSD, Edit Distance, Levenshtein Distance)
- A metric for measuring text entry accuracy by calculating the minimum number of single-character insertions, deletions, and substitutions needed to transform the transcribed text into the intended tex…
- Perplexity (Language Model Perplexity)
- A standard metric for evaluating language models that measures how well the model predicts a sample of text. Mathematically, perplexity is the inverse probability of the test set, normalised by the nu…
- SMOG (SMOG Index, SMOG Grade, Simple Measure of Gobbledygook)
- A readability formula developed by G. Harry McLaughlin in 1969 that estimates the years of education needed to understand a text, based on the number of polysyllabic words (three or more syllables) in…
- Sensitivity (Recall, Thoroughness, Completeness)
- In the context of accessibility evaluation, sensitivity (also called recall or thoroughness) is the proportion of true accessibility problems that are successfully identified and reported by an evalua…
- Text Entry Rate (Typing Speed, Characters Per Minute, CPM, Words Per Minute, WPM)
- A measure of how quickly a user can input text using a given method, typically expressed in words per minute (WPM) or characters per minute (CPM). One word is conventionally defined as five characters…
- Text Generation Rate (TGR, Text Entry Rate, Text Entry Speed)
- The speed at which a user produces text, typically measured in words per minute (WPM) or characters per second. Text generation rate is a key performance metric in assistive technology evaluation beca…
- Web Accessibility Barrier (WAB, Accessibility Barrier)
- Any element, design pattern, or technical implementation on a web page that prevents or hinders people with disabilities from accessing, understanding, or interacting with content. Common web accessib…
- Web Accessibility Barrier Score (WAB, WAB Score)
- A quantitative metric for measuring the accessibility level of a website, defined as the mean value of the failure rate of accessibility checkpoints on a page, weighted by the priority of each checkpo…