What is a percentile?
A percentile describes where a score sits relative to everyone else. If a candidate is in the 90th percentile, they scored at or above 90% of the cohort — regardless of what the raw mark was. It answers "how did I do compared to others?" rather than "how many did I get right?".
Percentiles are useful when relative standing matters more than an absolute mark — in competitive or norm-referenced settings, or when comparing across different exam versions. They come out of cohort analysis and sit alongside raw scores and grade bands in a full picture of performance.