Prerequisites for Mathematical Statistics. (SSC 384, Topic 2 and SSC 384, Topic 3)
Read about these in links from these two documents: Semester 1, Semester 2.
(Here's the direct link to the prerequisite discussion.)
In that discussion, be sure to follow the links to each of these and read about them:
After reading those (or at least skimming over them), if you would like to DO something, here is a set of activities. . Here's a reading list from an undergraduate math stat book.