Her reasoning is exactly the same in the case where Charlie prepares a spin singlet state at the center of the laboratory and sends the two particles in opposite directions towards apparatuses constructed by Alice and Bob, both competent experimentalists, and Alice measures \(S_{az}\). From her measurement outcome and because she is a competent experimentalist she is entitled to conclude that before the measurement took place particle \(a\) possessed the value indicated later by the pointer position; see the discussion in subsection 7.2. Assume for the sake of discussion that this was \(S_{az} = +1/2\). Then from her knowledge of the protocol (initial singlet state) she can assign a state \(S_{bz}=-1/2\) to Bob’s particle and use this (as a pre-probability) to assign a probability to the outcome of a measurement of \(S_{bz}\). She employs a scheme of probabilistic inference appropriate to the quantum world; there is no need to invoke wave function collapse except, perhaps, as a handy calculational tool.