"Evaluations" of Observables Versus Measurements in Quantum Theory

In Quantum Physics there are circumstances where the direct measurement of a given observable encounters difficulties; in some of these cases, however, its value can be "evaluated", i. e. it can be inferred by measuring another observable characterized by perfect correlation with the observable of interest. Though an evaluation is often interpreted as a measurement of the evaluated observable, we prove that the two concepts cannot be identified in Quantum Physics, because the identification yields contradictions. Then, we establish the conceptual status of evaluations in Quantum Theory and how they are related to measurements.