A quick and universally applicable spreadsheet method is outlined for the calculation of standard deviations based on the general formula for error propagation: S-R(2) = (partial derivative R/partial derivative X)(2) S-x(2) + (partial derivative R/partial derivative Y)(2) S-y(2) + (partial derivative R/partial derivative Z)(2) S-z(2) + ... With this method, standard deviations are calculated numerically without violating the condition of mutual independence, with a substantial time gain and with no risk of calculating errors. Satterthwaite's approximation of the degrees of freedom is a logical extension of the technique with which confidence intervals can be easily established. Direct insight is obtained about the separate contributions of the different error sources.
