Ordinary least squares:
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Minimizer is Linear / Migrad
Chi2                      =       606758
NDf                       =          246
p0                        =       15.724   +/-   0.0887641   
p1                        =    -0.835912   +/-   0.14096     
p2                        =     -3.40616   +/-   0.0607296   
p3                        =      4.82569   +/-   0.0602628   
Resistant Least trimmed squares fit:
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Minimizer is Linear / Robust (h=0.75)
Chi2                      =       634848
NDf                       =          246
p0                        =     0.997007
p1                        =      1.72222
p2                        =      2.97468
p3                        =      4.07139