 Bell presented several formulations of the theorem over the years (Bell 1964, 1971, 1976, 1990), and variants of it have been presented by others. The original derivation (1964) relied on a set-up involving perfect anticorrelation of the results of spin experiments on pairs of spin-1/2 particles prepared in the singlet state. Under this condition, the Bell locality condition entails that outcomes of experiments are predetermined by the complete specification of state, a condition which we will call outcome determinism (OD). Clauser, Horne, Shimony and Holt (1969) derived an inequality, the CHSH inequality, that does not require this assumption. Though in their proof they employed the condition OD, this condition is unnecessary for the derivation of the inequality, as shown by Bell (1971), who provided a proof of the CHSH inequality that relies on neither the assumption of perfect anticorrelation nor an assumption of outcome determinism. 