The quality of measured or observed values is described by the errors among those values, whereby a distinction is made between random and systematic errors. Random errors are dispersed, while systematic errors are essentially identifiable. Since random errors under identical measurement conditions differ in terms of value and sign (i.e., they are dispersed), “uncertainty” is introduced as the characterizing variable. The variable “inaccuracy” is used for the systematic errors. Generally speaking, the result of an error calculation is calculated from several influencing variables; that is to say, both random errors and systematic errors propagate. If there are limit values for the errors (error limits), the result error limits are calculated from these.