Hi I need help in understanding how does the parametric bootstrap confidence interval works. I have a step-stress model from gamma distribution, I plugged in the log-likelihood function to get the MLE`s of the three parameters alpha, theta1 and theta2. Now I need to find the parametric bootstrap Confidence intervals. I know that I should use first the boot function with sim='parametric' and ran.gen=?? but I dont understand what is the difference between the ran.gen and the statistics. Thank you and take care. Laila [[alternative HTML version deleted]]