Mark, you are correct, it does install packages globally. It's designed to complement the project-oriented approach of Leiningen and Maven, not replace it.
These slides are from a talk Mark Volkmann gave at the Strange Loop Conference, he has a more detailed article on Clojure's implementation of STM here: http://java.ociweb.com/mark/stm/article.html
The plots and chi-square tests are a single function each, it's the data preparation that takes up so much space. Alas, most statistical analyses involve a lot of preparatory steps, which are rarely shown in the final write-up.