Why can't use 'Fit Logistic 4P Rodbard' ?

[#1]

hi, why does the option 'Fit Logistic 4P Rodbard' gray out in my JMP(16.1.0)? Anyone know the reason？Thanks！

ChernoffTurtle7_0-1704939797607.png

[#2 · Accepted solution]

That model is disallowed when you have a dose equal to zero. Here is the result if that level is excluded and hidden:

dose.JPG

Some analysts use log dose, which is missing for dose equal to zero. This model is available in this case, too:

log dose.JPG

[#3]

thank you very much!