The most common approach is not to use parametric models due
to the following reasons:
1. Modern computers allow to handle the computations needed
using the collected data.
2. It is difficult to justify that a parametric model applies.
3. Knowing that a particular model applies we can get more
accurate estimates. But, this increase in accuracy is not much. If a
parametric model does not apply, using the parametric approach we
can get much worse estimates than the nonparametric estimates.