Bell–CHSH is an inequality about unconditional expectations: under measurement independence, Bell locality, and bounded outcomes, the CHSH value satisfies
. Experimental correlators, however, are often computed on an accepted subset of trials defined by detection logic, coincidence matching, quality cuts,
[...] Read more.
Bell–CHSH is an inequality about unconditional expectations: under measurement independence, Bell locality, and bounded outcomes, the CHSH value satisfies
. Experimental correlators, however, are often computed on an accepted subset of trials defined by detection logic, coincidence matching, quality cuts, and analysis windows. We model this by an acceptance probability
and the resulting accepted hidden-variable law
obtained by weighting the measurement-independent prior
by
and renormalizing. If
depends on the setting pair then the four correlators entering CHSH are expectations under four different measures, and a Bell-local measurement-independent model can yield
by selection alone. We quantify the required setting dependence in total variation (TV) distance. For any reference law
we prove the sharp bound
for a CHSH quartet
Q. Optimizing over
yields the intrinsic dispersion bound
, and, in particular,
, where
is the quartet TV diameter. The constants are optimal. Consequently, reproducing Tsirelson’s value
within Bell-local measurement-independent models via setting-dependent acceptance requires
(hence,
). We then propose a two-lane experimental audit protocol: (i) prior-relative fair-sampling diagnostics using tags recorded on all trials, and (ii) prior-free dispersion diagnostics using accepted-tag distributions across settings, with
computable by linear programming on finite tag alphabets.
Full article