Abstract: A system and a method for determining a concentration region for a measurement of a response value by means of a calibration curve is disclosed. The calibration curve includes response values as a function of concentrations. The method includes providing a series of measured calibration data; fitting a regression model to the series of measured calibration data; calculating a standard deviation and a standard error for the measured calibration data; calculating a probability using the t-distribution with parameters including degrees of freedom and a requested confidence interval; calculating a response value interval; applying the response value interval to the calibration model; measuring a response value for a sample; and determining the concentration region by means of the response value interval and the calibration model.