The invention provides a method for providing output values with associated uncertainties for a flexible modular plant or machine comprising an arrangement of modular entities (21-2n). To a plurality of said modular entities (21-2n), uncertainty information associated with an operation of said modular entity (21-2n) is assigned. Input values are provided based on an operation of the modular entities (21-2n). A computing unit (12) calculates an output value based on said input values. The computing unit (12) calculates an input value uncertainty for each input value based on the uncertainty information of the modular entity (21-2n). The computing unit (12) calculates at least one output value uncertainty associated with the output value based on propagation of uncertainty and using the input value uncertainties. The output value and the at least one output value uncertainty is outputted.