Extensive tests have shown, there is a very good agreement between the Co-variance estimation, and Monte-Carlo simulations.
This is indeed a very positive implementation.
task #7822(https://gna.org/task/index.php?7822): Implement user function to estimate R2eff and associated errors for exponential curve fitting.
bug #22554(https://gna.org/bugs/index.php?22554): The distribution of intensity with errors in Monte-Carlo simulations are markedly more narrow than expected.