I am doing some nonlinear regression and use mathematica to calculate the associated FitResiduals and StudentizedResiduals.
I am a bit confused right now because one studentized residual come out as a complex number...
According to the definition:
StRes=FitRes/[Estimated Variance*(1-Hatmatrix Diagonal number)]^0.5.
How can Estimated Variance*(1-Hatmatrix Diagonal number) be negative? Clearly there is something I do not understand about what mathematica exactly computes this...
Thanks in advance,