Hi group,
I am trying to reproduce a simple dose response analysis that I had performed in SPSS. So in JMP i am using the "Fit model" module, selecting for Generalized linear models, binomial distribution and probit link.
I have three variables, number of assays performed (10 assays), number of assays with positive result and concentration (from 0 to 36)
0 10 2
1 10 4
2 10 9
6 10 16
8 10 25
9 10 36
0 10 0
I select number of assays performed as "Y" variable, number of assays with positive result as "Freq" and concentration in logs as variable to model effects on. But when I hit run I get this message in the results:
"Warning: Hessian not positive definite. Singularity is likely due to a poor fit of the model, or linear dependencies among the model covariates. Fit and result are of questionable value"
And the analysis is not performed.
Can anyone share some comments?
Thanks,
Dave