When making decisions, we often encounter interval uncertainty, i.e. when the values of probabilities or other parameters are described by interval data. In this case, we are dealing with the interval value of the Expected Utility function. However, the solution of this problem with use of Moore arithmetic leads to a reduction in informativeness and, consequently, an increase in entropy. The use of the RDM interval arithmetic for the purpose of informativeness increasing seems to be an efficient approach for interval decision making.