There are other options for double logistic that allow a fixed level for the lower or upper tails, as opposed to them reaching zero. Im not suggesting we do it, but this may allow capturing older and younger ages better than the 4-parameter double logistic.
There are other options for double logistic that allow a fixed level for the lower or upper tails, as opposed to them reaching zero. Im not suggesting we do it, but this may allow capturing older and younger ages better than the 4-parameter double logistic.