I'm working on the effects of alternative larvicides on Aedes aegypti. Right now, I am doing binary mortality response with a single explanatory variable (dose) on 4 concentrations of one larvicide (+ control). Our university is fond of SPSS, and I have learned to conduct the basic probit model with it, including a natural logarithm transformation on my dosis data.
Not so long ago, I've started working with R, and through a combination of the 'glm' and 'dose.p' functions, I get the same slope and intercept, as well as LD50 calculations. Nevertheless, the standard errors and Z-scores calculated through the Probit model in SPSS comes out completely differently in R. Additionally, the 95% confidence intervals for the LD50 come out very differently between the two programs. I really don't have a clue on how I am getting the same slopes, intercepts and LD50's, but totally different SE, Z, and 95% CI. Can anybody help me so I can get the same results in R??