Hi Kate, try looking at the package 'drc' on CRAN and in particular look at the example in the help page for the dataset 'daphnids' (?daphnids).
You can obtain arbitrary ED values with approximate standard errors using the function 'ED'. Christian ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
