The notion of physical probability is connected to one of the major theories of statistical method, which has come to be called classical statistics.  It was developed roughly in the first half of the 20th century, mostly by mathematicians and working scientists like Fisher (1925, 1935, 1956), Wald (1939, 1950), Neyman and Pearson (1928, 1933, 1967), and refined by very many classical statisticians of the last few decades.  The key characteristic of this theory of statistics aligns naturally with viewing probabilities as physical chances, hence pertaining to observable and repeatable events. Physical probability cannot meaningfully be attributed to statistical hypotheses, since hypotheses do not have tendencies or frequencies with which they come about: they are categorically true or false, once and for all. Attributing probability to a hypothesis seems to entail that the probability is read epistemically.