Character; either "mean" (use the mean estimates of the
mean and standard deviation) or "sample" (randomly sample mean and
standard deviation from uncertainty given in the <dist_spec>
# An uncertain gamma distribution with mean 3 and sd 2dist <- LogNormal(
meanlog = Normal(3, 0.5), sdlog = Normal(2, 0.5), max = 20)
fix_parameters(dist)