If you use free LAB Fit Curve Fitting Software ( www.labfit.net ) to fit a function to your dataset, in dialog box "Results" you find: 1) average values of the parameters, 2) the corresponding uncertainties, 3) the covariance matrix. LAB Fit has an error propagation option (first order approximation). Using this option, you inform 1) the expression to determine the propagated error, 2) the average values, 3) the uncertainties, 4) the covariance matrix. See an complete example at: https://www.labfit.net/fitting.htm . If you insttall LAB Fit, see several videos clicking "Help" and choosing "Show Features (ppsx)". A general idea is available in https://www.youtube.com/@WiltonPereira-d9z

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