When I use the roofit to get fitting value and its error, the default method is likelihood method.
To get the fitting error, the likelihood value is floated in [-0.5, 0.5] range.
For me， I would like to set the range is [-1, 1]. Do you know the interface to set the range ?
Thank you in advance.
The fitting errors are computed by default from the inverse of the Hessian matrix (second derivatives of the likelihood functions).
They can be obtained, when using Minos, looking at the parameter change which gives a profiled likelihood value = minimum_value + 0.5.
It is not the range (-0.5,0.5).
If you want to change the scale of the errors, for example likelihood value at which they are computed (e.g. 1.96 instead of 0.5 for 2-sigma errors), you can use in RooFit, the method RooMinimizer::setErrorLevel or, if using ROOT, ROOT::Math::Minimizer::SetDefaultErrorLevel.