From your wording, it seems like your brain might have slipped gears when talking about probabilities, from 'science' mode to 'homo sapiens sapiens hardwired qu

From your wording, it seems like your brain might have slipped gears when talking about probabilities, from 'science' mode to 'homo sapiens sapiens hardwired quantity estimator' mode. When you say that "you can get that 25% increase purely by chance" do you mean (a) in better circumstances this should be formally impossible, or (b) the intra-observer variability is so high that there is significant (by some definition) possibility ___ of falsely detecting a 25% increase?