I am having a problem with betamix. Our dependent variable has a distribution whose characteristics are similar to the ones described in Pereira, Botter and Sandoval (2013) (https://journals.sagepub.com/doi/10....71082X13478274) with a fixed threshold (c): values in the range (0, 0.333) have been replaced by zero, so an inflation in zero occurs. Then we observe values in the interval [0.333,1], with a distribution skewed to the right.
We need to estimate:
  1. the discrete change in the probability of the dependent variable acquiring a value of zero (and its significance), given the values of a dummy variable (DUM). We attempted to use the mchange command, but it is invalid for betamix. The command does provide the odds ratio, but this is not the result we need.
  2. The difference in the mean value of the beta mixture part of the model strictly (without taking into account the zeros) conditional on DUM, and its significance. We attempted to calculate margins, but the mean we obtain takes into account the zeros in the lower bound, so it is not the information we need.
  3. The difference in the predicted value of the dependent variable as a whole, conditional on DUM. We are using the command “margin r.DUM” and we obtain the desired results and corresponding significance.
In our estimation, we include DUM as follows (where a=0.333):
betamix depvar, muvar(i.DUM …covariates…) pmvar(i.DUM …covariates…) lbound(0) ubound(1) trun(bottom) tbound(`a') pmass(0 0 1) vce(cluster var)
Can anyone please suggest some alternative command we can use to extract results (1) and (2) from the estimated model?