Sleep went from 5 hours to 7 and my solve rate doubled. Coincidence?

I tracked it for two weeks because I was tired of guessing. Before: late nights, around five hours of sleep, and roughly 1 problem in 4 solved without a hint. After: lights out before midnight, same study hours, and it's closer to 1 in 2. Tiny sample and I didn't change anything else, so I know it proves nothing. Curious whether anyone else noticed the same thing or if I'm just tired and bad at tracking.