for a thesis in the course "market research" at my university I should reproduce the results of the CBC/Logit analysis of a given conjoint study made with SSi-Web. For a deeper understanding of conjoint, my teachers said I should use the statistical software R.

Now my problem: With the effect coding of the data set, I conducted a maximum likelihood estimation with a existing R-function. I have nearly the same results as SSi but, now the problem, just 17 values from 23 attribute levels with 6 attributes (sum(levels) - #attributes). I know how to calculate the missing effects through the effects coding, but I do not understand how I can calculate the standard error of the missing part-worths in the estimation. Can you help me with this, please? Is there a way to calculate the missing standard errors from the estimated ones?