Abstract: A signal processing method in a processor is provided for performing a multicomponent analysis of a signal resulting from a spectral response of a mixture comprising a plurality of spectrally resolvable molecular species. The method provides both a determination of a concentration estimate and a statistical confidence interval for each species. In the method, a data vector d is received from a multichannel detector, data vector d having a length n.sub.c, n.sub.c being the number of detector channels being monitored. A calibration matrix K having n.sub.c rows and n.sub.p columns is provided wherein n.sub.c is larger than n.sub.p, n.sub.p being the number of spectrally resolvable molecular species. Next, a concentration estimate vector c having length n.sub.p is determined. Finally, a confidence interval CI.sub.i for each of the elements of the concentration estimate vector is determined according to the expressionCI.sub.i =c.sub.i .+-.(varcovar(c.sub.ii)).sup.1/2 Q.sub.