A solution to any problem is valuable only if the results of the solution are reliable. This axiomatic statement is trivial. However, despite the fact that this statement is undeniable, it is violated regularly in problems of operations research. This is due to the fact that the proposed evaluation criteria are not verified and possibility of using indirect methods of effectiveness evaluation of operations is not substantiated. The problem point of modeling was shown using the example of comparison of operational processes, based on equally effective operations with multiple duration. This point is related to the fact that it is necessary to take into account inter-operational losses while modeling the process, based on the use of shorter operations in relation to an alternative operational process. Ignoring these losses can lead to making a mistaken decision or to errors in verification of estimation indicators. In a number of cases the problem can be solved using specially conducted experimental studies. However, if there is a set of unverified estimation expressions or in verification problems, a formal approach can be used. Under this approach, uncertainty, arising in the process of modeling, can be removed by using the capabilities of a verified indicator itself. The developed method for modeling allows us to determine the scope of constraints on parameters of modeled operations. The probability of an error in results of modeling in problems, related to decision making, is excluded on condition of taking into account this region