### Ability comparison

Select two models to compare their abilities. The generated histogram
represents the distribution of the difference in estimated model
abilities. In the figure:

* The dashed vertical line is the median.
* The shaded region demarcates the chosen [highest density
  interval](https://cran.r-project.org/package=HDInterval) (HDI).
* The note in the upper left denotes the smallest HDI that is
  inclusive of $ci.