  When considering the connection between frequency and chance, not just any frequency will do. What is wanted is the frequency in relevantly similar trials, with the same kind of experimental setup. The relevance of frequencies in such trial is derived from the assumption that in such similar trials, the same chances exist: intra-world duplicate trials should have the same chances. This is closely related to the ‘stable trial principle’ (Schaffer, 2003: 37ff). Chances attach to the outcomes of trials, but the physical grounds of the chance lie in the physical properties of the trial device or chance setup.