probit

Posted by P. Hondelmann on Oct 24, 2006; 12:58pm
URL: http://spssx-discussion.165.s1.nabble.com/probit-tp1071648.html

Dear List,

although looking in the archive I did not find the solution. I use the
Probit analysis in SPSS 12G. I have count data ("response", I use simply
the observed amount of dead individuals) vs dosis ("covariate"), the output
looked first ok. But the problem is: If I use subgroups for different
treatments (as "factor" 1 to n) the results differ completely compared to
the results of separate analyses. And a second problem: How to compare
different probabilites, i.e. LT50 from treatment 1 with LT50 from treatment
2? I have no idea since this are not means...
Thanks a lot for any input.

Peter