 In its usual formulation the Born Rule does not look like a normative constraint on credences. QBists prefer to reformulate it purely as a relation among (subjective) probabilities without reference to a quantum state. In the form of Equation \((\ref{ex2})\) it relates probabilities \(q\) of actual measurement outcomes \(j\) to probabilities of outcomes of a hypothetical fiducial measurement of a special kind called a  SIC.[2]