Thanks for checking us out! We measure factual consistency using a NLP task known as "natural language inference". We then compare 2 sentences to know if one is an 'entailment' of another (for example - if "there are 3000 oranges in the supermarket", an entailment would be "there are oranges in the supermarket" - which would get a high score whereas "there are no oranges in the supermarket" would be a contradiction. We use the score of the entailment class to get a measure of how factually consistent it is. We provide a high-level summary in the documentation (https://docs.confident-ai.com/docs/measuring_llm_performance...) and will be sharing an in-depth blog article on it soon!