Empirical determination of the correlation coefficient between the number of counts in a peak in a gamma-ray spectrum and the number of counts in the continuum where the peak is superimposed

An account is given on the value of the correlation coefficient between the number of counts in a peak in a gamma-ray spectrum and the number of counts in the background, where the peak resides. It is supposed that the decomposition of the spectrum in the peak and in the background is performed by using the Least Squares method. The values of the correlation coefficient were determined empirically from measurements of gamma-ray spectra under repeatable conditions and from analyses of these spectra using four different kinds of peak-analysis software. These values were compared to the a-priori values, obtained from the Least Squares method. •The number of counts in the peak and the continuous background are correlated.•The value of the correlation coefficient is empirically determined.•The value depends on the width of the fitted region.•In case of short widths of the fitted region it tends to unity.