I want to fit a curve by means of logistic regression with the following parameters:
p(x) = exp(a + bx) / (1 + exp(a + bx)) with x: foil of a certain thickness and p(x): detection (yes / no). I want to estimate x for p(x)=1/2. This is a problem within psychometrics (psychophysics). But unlike the normal psychometric problems concerning discrimination, I would like to estimate the above mentionned threshold. This can be seen as being equivalent to a bio-assay problem. But in my case all observations (n=160) are made by one person (I have n=62 persons). Hence, they are dependent. But estimation within logistic regression requests independent observations. After my opinion the dependency of the observations do not influence the estimate itsself but rather its variance. But I am not sure. Who can give me some hints or literature?? Thank You in advance for your help. C. Nicolay, MS University of Bonn (Germany) . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
