# MATLAB: Confidence interval for positive value distribution with a large proportion of 0

confidence intervaltobit distributionwald test

Hi, Here is my situation: I have a sampling of 60 bills on a population of size 2500. On that sampling, 20 have an error, i.e they have been considered refundable when they were not, and 40 are OK. The bills have different amounts. I need to estimate with a confidence interval how much money should be reimbursed to correct for the errors that have been made.
I thought of using the Wald test to estimate a confidence interval around the probability of error I estimated from my sample (1/3). However, I want to take into account the variability of the amount in case of error too. I also thought of using the Tobit model, because I read such a model can be used for modeling a variable value that is 0 for a nontrivial fraction of the population and roughly continuously distributed over positive values. But since I don’t really have a independant variable to put in my model (I just have amount distribution), I don’t know what to do.