Questions on the way
What is an AI benchmark?
A fixed set of tasks or questions used to score models in the same way. Stanford's HELM, for example, scored 30 models on the same core scenarios under standardised conditions so they could be compared fairly.
How do arena-style leaderboards work?
A person asks a question, sees answers from two anonymous models and picks the better one. The votes feed a statistical model, the Bradley-Terry model, which turns many pairwise results into scores with confidence intervals.
What is benchmark contamination?
It is when questions from a test, or very similar ones, leak into a model's training data. The model can then score well partly from memory rather than skill, which is why researchers build fresh test sets.
Does a higher rank mean a model is better for me?
Not necessarily. Rankings average particular tests or many people's questions. The AI Index notes the top models are now very close, so trying a few of your own tasks often tells you more.
Are government AI evaluations the same as leaderboards?
No. The UK AI Security Institute tests systems for capabilities and risks, and says these evaluations give a snapshot of a system rather than a certificate that it is safe.