Additional information decreases the estimated entanglement using the Jaynes principle

We study a particular example considered in {[Phys. Rev. A {\bf 59,} 1799 (1999)]}, concerning the statistical inference of quantum entanglement using the Jaynes principle. Assume a Clauser-Horne-Simony-Holt (CHSH) Bell operator, a sum of two operators $\sqrt{2}(X+Z)$. Given only an average of the Bell-CHSH operator, we may overestimate entanglement. However, the estimated entanglement is decreased (never increases) when we use the expectation value of the operator $X$ as additional information. A minimum entanglement state is obtained by minimizing the variance of the observable $X$.