

@rastilin is making some unproven assumptions here. But it is true that the “math question” dataset consists only of prime numbers, so if the first version thought every number was prime and the second thought no numbers were prime, we would see this exact behavior. Source:
For this dataset, we query the primality of 500 randomly chosen primes between 1,000 and 20,000; the correct answer is always Yes.
From Zhang et al. (2023), the paper they took the dataset from.
True, GPT does not return a “yes” or “no” 100% of the time in either case, but that’s not the point. The point is that it’s impossible to say if GPT has actually gotten better or worse at predicting prime numbers with their test set. Since the test set is composed of only prime numbers, we do not know if GPT is more likely to call a number “prime” when it actually is a prime number than when it isn’t. All we know is that it was very likely to answer “yes” to the question “is this number prime?” in March, and very likely to answer “no” in July. We do not know if the number makes a difference.